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  • For general information about writing shell scripts, read Shell Scripting Primer.



KSH(1)                                                                                                KSH(1)



NAME
       ksh, rksh, pfksh - KornShell, a standard/restricted command and programming language

NOTE
       Currently, rksh and pfksh are not available on Mac OS X / Darwin.

SYNOPSIS
       ksh [ +-abcefhikmnoprstuvxBCDP ] [ -R file ] [ +-o option ] ... [ - ] [ arg ... ]
       rksh [ +-abcefhikmnoprstuvxBCD ] [ -R file ] [ +-o option ] ...  [ - ] [ arg ... ]

DESCRIPTION
       Ksh  is  a  command  and  programming language that executes commands read from a terminal or a file.
       Rksh is a restricted version of the command interpreter ksh; it is used to set  up  login  names  and
       execution  environments  whose  capabilities  are  more  controlled than those of the standard shell.
       Rpfksh is a profile shell version of the command interpreter ksh; it is used to to  execute  commands
       with  the  attributes specified by the user's profiles (see pfexec(1)).  See Invocation below for the
       meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

              ;   &   (   )   |   <   >   new-line   space   tab

       A blank is a tab or a space.  An identifier is a sequence of letters, digits, or underscores starting
       with  a  letter  or  underscore.  Identifiers are used as components of variable names.  A vname is a
       sequence of one or more identifiers separated by a . and optionally preceded by a ..  Vnames are used
       as function and variable names.  A word is a sequence of characters from the character set defined by
       the current locale, excluding non-quoted metacharacters.

       A command is a sequence of characters in the syntax of the shell language.  The shell reads each com-mand command
       mand  and carries out the desired action either directly or by invoking separate utilities.  A built-in builtin
       in command is a command that is carried out by the shell itself without creating a separate  process.
       Some  commands are built-in purely for convenience and are not documented here.  Built-ins that cause
       side effects in the shell environment and built-ins that are found before performing  a  path  search
       (see  Execution  below)  are documented here.  For historical reasons, some of these built-ins behave
       differently than other built-ins and are called special built-ins.

   Commands.
       A simple-command is a list of variable assignments (see Variable Assignments below) or a sequence  of
       blank  separated  words  which  may  be  preceded  by a list of variable assignments (see Environment
       below).  The first word specifies the name of the command to be executed.  Except as specified below,
       the  remaining  words  are passed as arguments to the invoked command.  The command name is passed as
       argument 0 (see exec(2)).  The value of a simple-command is its exit status; 0-255 if  it  terminates
       normally;  256+signum  if  it terminates abnormally (the name of the signal corresponding to the exit
       status can be obtained via the -l option of the kill built-in utility).

       A pipeline is a sequence of one or more commands separated by |.  The standard output of each command
       but  the  last  is  connected  by a pipe(2) to the standard input of the next command.  Each command,
       except possibly the last, is run as a separate process; the shell waits for the last command to  ter-minate. terminate.
       minate.   The  exit  status  of a pipeline is the exit status of the last command unless the pipefail
       option is enabled.  Each pipeline can be preceded by the reserved word !  which causes the exit  sta-tus status
       tus of the pipeline to become 0 if the exit status of the last command is non-zero, and 1 if the exit
       status of the last command is 0.

       A list is a sequence of one or more pipelines separated by ;, &, |&, &&, or ||, and optionally termi-nated terminated
       nated by ;, &, or |&.  Of these five symbols, ;, &, and |& have equal precedence, which is lower than
       that of && and ||.  The symbols && and || also have equal precedence.  A semicolon (;) causes sequen-tial sequential
       tial  execution of the preceding pipeline; an ampersand (&) causes asynchronous execution of the pre-ceding preceding
       ceding pipeline (i.e., the shell does not wait for that pipeline to finish).  The  symbol  |&  causes
       asynchronous execution of the preceding pipeline with a two-way pipe established to the parent shell;
       the standard input and output of the spawned pipeline can be written to and read from by  the  parent
       shell  by  applying the redirection operators <& and >& with arg p to commands and by using -p option
       of the built-in commands read and print described later.  The symbol && (||) causes the list  follow-ing following
       ing  it  to  be executed only if the preceding pipeline returns a zero (non-zero) value.  One or more
       new-lines may appear in a list instead of a semicolon, to delimit a command.  The first item  of  the
       first pipeline of a list that is a simple command not beginning with a redirection, and not occurring
       within a while, until, or if list, can be preceded by a semicolon.  This semicolon is ignored  unless
       the showme option is enabled as described with the set built-in below.

       A  command  is  either  a simple-command or one of the following.  Unless otherwise stated, the value
       returned by a command is that of the last simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
              Each time a for command is executed, vname is set to the next word  taken  from  the  in  word
              list.   If  in  word  ...  is omitted, then the for command executes the do list once for each
              positional parameter that is set starting from 1 (see Parameter Expansion  below).   Execution
              ends when there are no more words in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
              The  arithmetic  expression  expr1  is evaluated first (see Arithmetic evaluation below).  The
              arithmetic expression expr2 is repeatedly evaluated until it evaluates to zero and  when  non-zero, nonzero,
              zero,  list  is  executed and the arithmetic expression expr3 evaluated.  If any expression is
              omitted, then it behaves as if it evaluated to 1.

       select vname [ in word ... ] ;do list ;done
              A select command prints on standard error (file descriptor 2) the set of words, each  preceded
              by  a  number.  If in word ...  is omitted, then the positional parameters starting from 1 are
              used instead (see Parameter Expansion below).  The PS3 prompt is printed and a  line  is  read
              from the standard input.  If this line consists of the number of one of the listed words, then
              the value of the variable vname is set to the word corresponding to this number.  If this line
              is  empty,  the selection list is printed again.  Otherwise the value of the variable vname is
              set to null.  The contents of the line read from standard  input  is  saved  in  the  variable
              REPLY.   The  list is executed for each selection until a break or end-of-file is encountered.
              If the REPLY variable is set to null by the execution of list,  then  the  selection  list  is
              printed before displaying the PS3 prompt for the next selection.

       case word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac
              A  case  command  executes  the list associated with the first pattern that matches word.  The
              form of the patterns is the same as that used for file-name generation (see File Name  Genera-tion Generation
              tion  below).   The ;; operator causes execution of case to terminate.  If ;& is used in place
              of ;; the next subsequent list, if any,  is executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
              The list following if is executed and, if it returns a zero exit status,  the  list  following
              the  first then is executed.  Otherwise, the list following elif is executed and, if its value
              is zero, the list following the next then is executed.  Failing each successive elif list, the
              else  list  is  executed.   If the if list has non-zero exit status and there is no else list,
              then the if command returns a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
              A while command repeatedly executes the while list and, if the exit status of the last command
              in  the  list is zero, executes the do list; otherwise the loop terminates.  If no commands in
              the do list are executed, then the while command returns a zero exit status; until may be used
              in place of while to negate the loop termination test.

       ((expression))
              The expression is evaluated using the rules for arithmetic evaluation described below.  If the
              value of the arithmetic expression is non-zero, the exit status is 0, otherwise the exit  sta-tus status
              tus is 1.

       (list)
              Execute  list  in  a  separate  environment.   Note, that if two adjacent open parentheses are
              needed for nesting, a space must be inserted to avoid evaluation as an arithmetic  command  as
              described above.

       { list;}
              list  is  simply  executed.  Note that unlike the metacharacters ( and ), { and } are reserved
              words and must occur at the beginning of a line or after a ; in order to be recognized.

       [[ expression ]]
              Evaluates expression and returns a zero exit status when expression is true.  See  Conditional
              Expressions below, for a description of expression.

       function varname { list ;}
       varname () { list ;}
              Define  a  function which is referenced by varname.  A function whose varname contains a .  is
              called a discipline function and the portion of the varname preceding the last .   must  refer
              to an existing variable.  The body of the function is the list of commands between { and }.  A
              function defined with the function varname syntax can also be used as an  argument  to  the  .
              special  built-in  command to get the equivalent behavior as if the varname() syntax were used
              to define it.  (See Functions below.)

       namespace identifier { list ;}
              Defines or uses the name space identifier^ and runs the commands in list^ in this name  space.
              (See Name Spaces below.)

       & [ name [ arg... ]  ]
              Causes  subsequent list commands terminated by & to be placed in the background job pool name.
              If name is omitted a default unnamed pool is used.  Commands in a named background pool may be
              executed remotely.

       time [ pipeline ]
              If pipeline is omitted the user and system time for the current shell and completed child pro-cesses processes
              cesses is printed on standard error.  Otherwise, pipeline is executed and the elapsed time  as
              well  as  the user and system time are printed on standard error.  The TIMEFORMAT variable may
              be set to a format string that specifies how the timing information should be displayed.   See
              Shell Variables below for a description of the TIMEFORMAT variable.

       The  following  reserved words are recognized as reserved only when they are the first word of a com-mand command
       mand and are not quoted:

       if then else elif fi case esac for while until do done { } function select time [[ ]] !

   Variable Assignments.
       One or more variable assignments can start a simple command or can be arguments to the typeset, enum,
       export,  or  readonly  special  built-in commands as well as to other declaration commands created as
       types.  The syntax for an assignment is of the form:

       varname=word
       varname[word]=word
              No space is permitted between varname and the = or between = and word.

       varname=(assign_list)
              No space is permitted between varname and the =.  An assign_list can be one of the following:
                      word ...
                             Indexed array assignment.
                      [word]=word ...
                             Associative array assignment.  If preceded by typeset -a this  will  create  an
                             indexed array instead.
                      assignment ...
                             Compound  variable  assignment.   This creates a compound variable varname with
                             sub-variables of the form varname.name, where  name  is  the  name  portion  of
                             assignment.   The  value  of  varname will contain all the assignment elements.
                             Additional assignments made to sub-variables of varname will also be  displayed
                             as part of the value of varname.  If no assignments are specified, varname will
                             be a compound variable allowing subsequence child elements to be defined.
                      typeset [options] assignment ...
                             Nested variable assignment.  Multiple assignments can be specified by  separat-ing separating
                             ing  each of them with a ;.  The previous value is unset before the assignment.
                             Other declaration commands such as readonly, enum, and other  declaration  com-mands commands
                             mands can be used in place of typeset.
                      . filename
                             Include the assignment commands contained in filename.

       In  addition,  a  +=  can be used in place of the = to signify adding to or appending to the previous
       value.  When += is applied to an arithmetic type, word is evaluated as an arithmetic  expression  and
       added to the current value.  When applied to a string variable, the value defined by word is appended
       to the value.  For compound assignments, the previous value is not  unset  and  the  new  values  are
       appended to the current ones provided that the types are compatible.

       The  right  hand  side  of a variable assignment undergoes all the expansion listed below except word
       splitting, brace expansion, and file name generation.  When the left hand side is an assignment is  a
       compound variable and the right hand is the name of a compound variable, the compound variable on the
       right will be copied or appended to the compound variable on the left.

   Comments.
       A word beginning with # causes that word and all the following characters up  to  a  new-line  to  be
       ignored.
   Aliasing.
       The first word of each command is replaced by the text of an alias if an alias for this word has been
       defined.  An alias name consists of any number of characters excluding metacharacters, quoting  char-acters, characters,
       acters,  file  expansion  characters, parameter expansion and command substitution characters, and =.
       The replacement string can contain any valid shell script including the metacharacters listed  above.
       The  first word of each command in the replaced text, other than any that are in the process of being
       replaced, will be tested for aliases.  If the last character of the alias value is a blank  then  the
       word  following  the alias will also be checked for alias substitution.  Aliases can be used to rede-fine redefine
       fine built-in commands but cannot be used to redefine the reserved words listed above.   Aliases  can
       be created and listed with the alias command and can be removed with the unalias command.
       Aliasing is performed when scripts are read, not while they are executed.  Therefore, for an alias to
       take effect, the alias definition command has to be executed before the command which references  the
       alias is read.
       The following aliases are compiled into the shell but can be unset or redefined:
                           autoload='typeset -fu'
                           command='command  '
                           compound='typeset -C'
                           fc=hist
                           float='typeset -lE'
                           functions='typeset -f'
                           hash='alias -t --'
                           history='hist -l'
                           integer='typeset -li'
                           nameref='typeset -n'
                           nohup='nohup  '
                           r='hist -s'
                           redirect='command exec'
                           source='command .'
                           stop='kill -s STOP'
                           suspend='kill -s STOP $$'
                           times='{ { time;} 2>&1;}'
                           type='whence -v'

   Tilde Substitution.
       After  alias  substitution is performed, each word is checked to see if it begins with an unquoted ~.
       For tilde substitution, word also refers to the word portion of parameter  expansion  (see  Parameter
       Expansion below).  If it does, then the word up to a / is checked to see if it matches a user name in
       the password database (See getpwname(3).)  If a match is found, the ~ and the matched login name  are
       replaced by the login directory of the matched user.  If no match is found, the original text is left
       unchanged.  A ~ by itself, or in front of a /, is replaced by $HOME.  A ~ followed by a  +  or  -  is
       replaced by the value of $PWD and $OLDPWD respectively.

       In  addition, when expanding a variable assignment, tilde substitution is attempted when the value of
       the assignment begins with a ~, and when a ~ appears after a :.  The :  also  terminates  a  ~  login
       name.

   Command Substitution.
       The  standard  output from a command list enclosed in parentheses preceded by a dollar sign ( $(list)
       ), or in a brace group preceded by a dollar sign ( ${ list;} ), or in a pair of  grave  accents  (``)
       may  be used as part or all of a word; trailing new-lines are removed.  In the second case, the { and
       } are treated as a reserved words so that { must be followed by a blank and  }  must  appear  at  the
       beginning  of the line or follow a ;.  In the third (obsolete) form, the string between the quotes is
       processed for special quoting characters before the command is executed  (see  Quoting  below).   The
       command  substitution $(cat file) can be replaced by the equivalent but faster $(<file).  The command
       substitution $(n<#) will expand to the current byte offset for file descriptor  n.   Except  for  the
       second  form,  the  command  list is run in a subshell so that no side effects are possible.  For the
       second form, the final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An arithmetic expression enclosed in double parentheses preceded by  a  dollar  sign  (  $(())  )  is
       replaced by the value of the arithmetic expression within the double parentheses.

   Process Substitution.
       This  feature  is  only  available  on versions of the UNIX operating system that support the /dev/fd
       directory for naming open files.  Each command argument of the  form  <(list)  or  >(list)  will  run
       process list asynchronously connected to some file in /dev/fd.  The name of this file will become the
       argument to the command.  If the form with > is selected then writing on this file will provide input
       for  list.   If  <  is  used, then the file passed as an argument will contain the output of the list
       process.  For example,

              paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(process2)

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes  the  results  together,  and
       sends  it  to  the  processes  process1 and process2, as well as putting it onto the standard output.
       Note that the file, which is passed as an argument to the command, is a UNIX pipe(2) so programs that
       expect to lseek(2) on the file will not work.

       Process  substitution  of  the  form  <(list)  can also be used with the < redirection operator which
       causes the output of list to be standard input or the input for whatever file  descriptor  is  speci-
       fied.

   Parameter Expansion.
       A  parameter  is a variable, one or more digits, or any of the characters *, @, #, ?, -, $, and !.  A
       variable is denoted by a vname.  To create a variable whose vname contains  a  .,  a  variable  whose
       vname  consists  of everything before the last . must already exist.  A variable has a value and zero
       or more attributes.  Variables can be assigned values and attributes by  using  the  typeset  special
       built-in command.  The attributes supported by the shell are described later with the typeset special
       built-in command.  Exported variables pass values and attributes to the environment.

       The shell supports both indexed and associative arrays.  An element of an array  variable  is  refer-enced referenced
       enced  by  a subscript.  A subscript for an indexed array is denoted by an arithmetic expression (see
       Arithmetic evaluation below) between a [ and a  ].   To  assign  values  to  an  indexed  array,  use
       vname=(value  ...)  or set -A vname  value ... .  The value of all non-negative subscripts must be in
       the range of 0 through 4,194,303.  A negative subscript is treated as an offset from the maximum cur-rent current
       rent  index  +1  so  that  -1 refers to the last element.  Indexed arrays can be declared with the -a
       option to typeset.  Indexed arrays need not be declared.  Any reference to a variable  with  a  valid
       subscript is legal and an array will be created if necessary.

       An  associative array is created with the -A option to typeset.  A subscript for an associative array
       is denoted by a string enclosed between [ and ].

       Referencing any array without a subscript is equivalent to referencing the array with subscript 0.

       The value of a variable may be assigned by writing:

              vname=value [ vname=value ] ...

       or
              vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       A nameref is a variable that is a reference to another variable.  A nameref is created  with  the  -n
       attribute of typeset.  The value of the variable at the time of the typeset command becomes the vari-able variable
       able that will be referenced whenever the nameref variable is used.  The name  of  a  nameref  cannot
       contain  a  ..   When a variable or function name contains a ., and the portion of the name up to the
       first . matches the name of a nameref, the variable referred to is obtained by replacing the  nameref
       portion  with  the name of the variable referenced by the nameref.  If a nameref is used as the index
       of a for loop, a name reference is established for each item in the list.  A nameref provides a  con-venient convenient
       venient way to refer to the variable inside a function whose name is passed as an argument to a func-tion. function.
       tion.  For example, if the name of a variable is passed as the first argument to a function, the com-mand command
       mand
              typeset -n var=$1
       inside  the function causes references and assignments to var to be references and assignments to the
       variable whose name has been passed to the function.
       If any of the floating point attributes, -E, -F, or -X, or the integer  attribute,  -i,  is  set  for
       vname, then the value is subject to arithmetic evaluation as described below.
       Positional  parameters,  parameters  denoted by a number, may be assigned values with the set special
       built-in command.  Parameter $0 is set from argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
              The shell reads all the characters from ${ to the matching } as part of the same word even  if
              it  contains  braces  or  metacharacters.  The value, if any, of the parameter is substituted.
              The braces are required when parameter is followed by a letter, digit, or underscore  that  is
              not  to  be  interpreted as part of its name, when the variable name contains a ..  The braces
              are also required when a variable is subscripted unless it is part of an Arithmetic Expression
              or  a  Conditional  Expression.   If  parameter  is one or more digits then it is a positional
              parameter.  A positional parameter of more than one digit must  be  enclosed  in  braces.   If
              parameter  is  *  or  @, then all the positional parameters, starting with $1, are substituted
              (separated by a field separator character).  If an array vname with subscript * @, or  of  the
              form  sub1  ..   sub2.  is used, then the value for each of the elements between sub1 and sub2
              inclusive (or all elements for * and @) is substituted, separated by the  first  character  of
              the value of IFS.
       ${#parameter}
              If  parameter  is  * or @, the number of positional parameters is substituted.  Otherwise, the
              length of the value of the parameter is substituted.
       ${#vname[*]}
       ${#vname[@]}
              The number of elements in the array vname is substituted.

       ${@vname}
              Expands to the type name (See Type Variables  below) or attributes of the variable referred to
              by vname.
       ${!vname}
              Expands  to  the  name  of  the variable referred to by vname.  This will be vname except when
              vname is a name reference.
       ${!vname[subscript]}
              Expands to name of the subscript unless subscript is *, @.  or of  the  form  sub1  ..   sub2.
              When subscript is *, the list of array subscripts for vname is generated.  For a variable that
              is not an array, the value is 0 if the variable is set.  Otherwise it is null.  When subscript
              is  @,  same  as  above, except that when used in double quotes, each array subscript yields a
              separate argument.  When subscript is of the form sub1 ..  sub2 it expands to the list of sub-scripts subscripts
              scripts between sub1 and sub2 inclusive using the same quoting rules as @.
       ${!prefix*}
              Expands to the names of the variables whose names begin with prefix.
       ${parameter:-word}
              If parameter is set and is non-null then substitute its value; otherwise substitute word.
       ${parameter:=word}
              If  parameter  is  not  set or is null then set it to word; the value of the parameter is then
              substituted.  Positional parameters may not be assigned to in this way.
       ${parameter:?word}
              If parameter is set and is non-null then substitute its value; otherwise, print word and  exit
              from the shell (if not interactive).  If word is omitted then a standard message is printed.
       ${parameter:+word}
              If parameter is set and is non-null then substitute word; otherwise substitute nothing.
       In  the  above,  word is not evaluated unless it is to be used as the substituted string, so that, in
       the following example, pwd is executed only if d is not set or is null:
              print ${d:-$(pwd)}
       If the colon ( : ) is omitted from the above expressions, then the shell only checks whether  parame-ter parameter
       ter is set or not.
       ${parameter:offset:length}
       ${parameter:offset}
              Expands  to  the portion of the value of parameter starting at the character (counting from 0)
              determined by expanding offset as an arithmetic expression and consisting  of  the  number  of
              characters determined by the arithmetic expression defined by length.  In the second form, the
              remainder of the value is used.  If A negative offset counts backwards from the end of parame-ter. parameter.
              ter.   Note  that one or more blanks is required in front of a minus sign to prevent the shell
              from interpreting the operator as :-.  If parameter is * or @, or is an array name indexed  by
              *  or  @, then offset and length refer to the array index and number of elements respectively.
              A negative offset is taken relative to one greater than  the  highest  subscript  for  indexed
              arrays.  The order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
              If  the  shell pattern matches the beginning of the value of parameter, then the value of this
              expansion is the value of the parameter with the matched portion deleted; otherwise the  value
              of  this parameter is substituted.  In the first form the smallest matching pattern is deleted
              and in the second form the largest matching pattern is deleted.  When parameter is @, *, or an
              array  variable  with  subscript @ or *, the substring operation is applied to each element in
              turn.

       ${parameter%pattern}
       ${parameter%%pattern}
              If the shell pattern matches the end of the value of parameter, then the value of this  expan-sion expansion
              sion  is  the  value  of the parameter with the matched part deleted; otherwise substitute the
              value of parameter.  In the first form the smallest matching pattern is  deleted  and  in  the
              second  form  the  largest  matching  pattern is deleted.  When parameter is @, *, or an array
              variable with subscript @ or *, the substring operation is applied to each element in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
              Expands parameter and replaces the longest match of  pattern  with  the  given  string.   Each
              occurrence  of \n in string is replaced by the portion of parameter that matches the n-th sub-pattern. subpattern.
              pattern.  In the first form, only the first occurrence of pattern is replaced.  In the  second
              form,  each  match  for pattern is replaced by the given string.  The third form restricts the
              pattern match to the beginning of the string while the fourth form restricts the pattern match
              to the end of the string.  When string is null, the pattern will be deleted and the / in front
              of string may be omitted.  When parameter is @, *, or an array variable with subscript @ or *,
              the  substitution operation is applied to each element in turn.  In this case, the string por-tion portion
              tion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
              #      The number of positional parameters in decimal.
              -      Options supplied to the shell on invocation or by the set command.
              ?      The decimal value returned by the last executed command.
              $      The process number of this shell.
              _      Initially, the value of _ is an absolute pathname of the shell or script being executed
                     as  passed  in  the  environment.  Subsequently it is assigned the last argument of the
                     previous command.  This parameter is not set for commands which are asynchronous.  This
                     parameter  is  also  used  to hold the name of the matching MAIL file when checking for
                     mail.  While defining a compound variable or a type, _ is initialized as a reference to
                     the compound variable or type.  When a discipline function is invoked, _ is initialized
                     as a reference to the variable associated with the call to this function.  Finally when
                     _  is  used  as  the  name  of the first variable of a type definition, the new type is
                     derived from the type of the first variable (See Type Variables  below.).
              !      The process id or the pool name and job number of the last background  command  invoked
                     or  the most recent job put in the background with the bg built-in command.  Background
                     jobs started in a named pool will be in the form pool.number where  pool  is  the  pool
                     name and number is the job number within that pool.
              .sh.command
                     When  processing  a DEBUG trap, this variable contains the current command line that is
                     about to run.
              .sh.edchar
                     This variable contains the value of the keyboard character (or sequence  of  characters
                     if  the  first  character is an ESC, ascii 033) that has been entered when processing a
                     KEYBD trap (see Key Bindings below).  If the value is  changed  as  part  of  the  trap
                     action, then the new value replaces the key (or key sequence) that caused the trap.
              .sh.edcol
                     The character position of the cursor at the time of the most recent KEYBD trap.
              .sh.edmode
                     The  value is set to ESC when processing a KEYBD trap while in vi insert mode.  (See Vi
                     Editing Mode  below.)  Otherwise, .sh.edmode is null when processing a KEYBD trap.
              .sh.edtext
                     The characters in the input buffer at the time of the  most  recent  KEYBD  trap.   The
                     value is null when not processing a KEYBD trap.
              .sh.file
                     The pathname of the file than contains the current command.
              .sh.fun
                     The name of the current function that is being executed.
              .sh.level
                     Set  to  the  current function depth.  This can be changed inside a DEBUG trap and will
                     set the context to the specified level.
              .sh.lineno
                     Set during a DEBUG trap to the line number for the caller of each function.
              .sh.match
                     An indexed array which stores the most recent match and sub-pattern matches after  con-ditional conditional
                     ditional  pattern matches that match and after variables expansions using the operators
                     #, %, or /.  The 0-th element stores the complete match and the i-th.   element  stores
                     the  i-th  submatch.   The  .sh.match variable becomes unset when the variable that has
                     expanded is assigned a new value.
              .sh.math
                     Used for defining arithmetic functions (see Arithmetic evaluation below).   and  stores
                     the list of user defined arithmetic functions.
              .sh.name
                     Set to the name of the variable at the time that a discipline function is invoked.
              .sh.subscript
                     Set  to  the  name  subscript of the variable at the time that a discipline function is
                     invoked.
              .sh.subshell
                     The current depth for subshells and command substitution.
              .sh.value
                     Set to the value of the variable at the time that the set or append discipline function
                     is invoked.  When a user defined arithmetic function is invoked, the value of .sh.value
                     is saved and .sh.value is set to long double precission floating point.   .sh.value  is
                     restored when the function returns.
              .sh.version
                     Set to a value that identifies the version of this shell.
              KSH_VERSION
                     A name reference to .sh.version.
              LINENO The current line number within the script or function being executed.
              OLDPWD The previous working directory set by the cd command.
              OPTARG The value of the last option argument processed by the getopts built-in command.
              OPTIND The index of the last option argument processed by the getopts built-in command.
              PPID   The process number of the parent of the shell.
              PWD    The present working directory set by the cd command.
              RANDOM Each  time this variable is referenced, a random integer, uniformly distributed between
                     0 and 32767, is generated.  The sequence  of  random  numbers  can  be  initialized  by
                     assigning a numeric value to RANDOM.
              REPLY  This  variable  is set by the select statement and by the read built-in command when no
                     arguments are supplied.
              SECONDS
                     Each time this variable is referenced, the number of seconds since shell invocation  is
                     returned.  If this variable is assigned a value, then the value returned upon reference
                     will be the value that was assigned plus the number of seconds since the assignment.
              SHLVL  An integer variable the is incremented each time the shell is invoked and is  exported.
                     If SHLVL is not in the environment when the shell is invoked, it is set to 1.

       The following variables are used by the shell:
              CDPATH The search path for the cd command.
              COLUMNS
                     If  this  variable is set, the value is used to define the width of the edit window for
                     the shell edit modes and for printing select lists.
              EDITOR If the VISUAL variable is not set, the value of this variable will be checked  for  the
                     patterns  as described with VISUAL below and the corresponding editing option (see Spe-cial Special
                     cial Command set below) will be turned on.
              ENV    If this variable is set, then parameter expansion, command substitution, and arithmetic
                     substitution  are  performed  on  the value to generate the pathname of the script that
                     will be executed when the shell is invoked interactively (see Invocation below).   This
                     file  is  typically  used  for  alias  and  function definitions.  The default value is
                     $HOME/.kshrc.  On systems that support a  system  wide   /etc/ksh.kshrc  initialization
                     file,  if  the  filename  generated by the expansion of ENV begins with /./ or ././ the
                     system wide initialization file will not be executed.
              FCEDIT Obsolete name for the default editor name for the hist command.   FCEDIT  is  not  used
                     when HISTEDIT is set.
              FIGNORE
                     A  pattern that defines the set of filenames that will be ignored when performing file-name filename
                     name matching.
              FPATH  The search path for function definitions.  The directories in this  path  are  searched
                     for  a  file  with the same name as the function or command when a function with the -u
                     attribute is referenced and when a command is not found.  If an  executable  file  with
                     the name of that command is found, then it is read and executed in the current environ-ment. environment.
                     ment.  Unlike PATH, the current directory must be represented explicitly by  .   rather
                     than by adjacent : characters or a beginning or ending :.
              HISTCMD
                     Number of the current command in the history file.
              HISTEDIT
                     Name for the default editor name for the hist command.
              HISTFILE
                     If  this  variable  is set when the shell is invoked, then the value is the pathname of
                     the file that will be used to store the command history (see Command Re-entry below).
              HISTSIZE
                     If this variable is set when the shell  is  invoked,  then  the  number  of  previously
                     entered  commands  that  are  accessible by this shell will be greater than or equal to
                     this number.  The default is 512.
              HOME   The default argument (home directory) for the cd command.
              IFS    Internal field separators, normally space, tab, and new-line that are used to  separate
                     the  results of command substitution or parameter expansion and to separate fields with
                     the built-in command read.  The first character of the IFS variable is used to separate
                     arguments  for the "$*" substitution (see Quoting below).  Each single occurrence of an
                     IFS character in the string to be split, that is not in the  isspace  character  class,
                     and  any  adjacent characters in IFS that are in the isspace character class, delimit a
                     field.  One or more characters in IFS that  belong  to  the  isspace  character  class,
                     delimit  a  field.   In  addition,  if the same isspace character appears consecutively
                     inside IFS, this character is treated as if it were not in the isspace class,  so  that
                     if  IFS consists of two tab characters, then two adjacent tab characters delimit a null
                     field.
              JOBMAX This variable defines the maximum number running background jobs  that  can  run  at  a
                     time.   When  this  limit  is reached, the shell will wait for a job to complete before
                     staring a new job.
              LANG   This variable determines the locale category for any category not specifically selected
                     with a variable starting with LC_ or LANG.
              LC_ALL This variable overrides the value of the LANG variable and any other LC_ variable.
              LC_COLLATE
                     This variable determines the locale category for character collation information.
              LC_CTYPE
                     This  variable  determines  the  locale  category for character handling functions.  It
                     determines the character classes for pattern matching (see File Name Generation below).
              LC_NUMERIC
                     This variable determines the locale category for the decimal point character.
              LINES  If  this variable is set, the value is used to determine the column length for printing
                     select lists.  Select lists will print vertically until about two-thirds of LINES lines
                     are filled.
              MAIL   If  this  variable  is  set to the name of a mail file and the MAILPATH variable is not
                     set, then the shell informs the user of arrival of mail in the specified file.
              MAILCHECK
                     This variable specifies how often (in seconds) the shell will check for changes in  the
                     modification time of any of the files specified by the MAILPATH or MAIL variables.  The
                     default value is 600 seconds.  When the time has elapsed the shell  will  check  before
                     issuing the next prompt.
              MAILPATH
                     A  colon  (  : ) separated list of file names.  If this variable is set, then the shell
                     informs the user of any modifications to the specified files that have occurred  within
                     the  last MAILCHECK seconds.  Each file name can be followed by a ?  and a message that
                     will be printed.  The message will undergo parameter expansion,  command  substitution,
                     and  arithmetic  substitution with the variable $_ defined as the name of the file that
                     has changed.  The default message is you have mail in $_.
              PATH   The search path for commands (see Execution below).  The user may not  change  PATH  if
                     executing under rksh (except in .profile).
              PS1    The  value  of this variable is expanded for parameter expansion, command substitution,
                     and arithmetic substitution to define the primary prompt string  which  by  default  is
                     ``$''.  The character !  in the primary prompt string is replaced by the command number
                     (see Command Re-entry below).  Two successive occurrences of !  will produce a single !
                     when the prompt string is printed.
              PS2    Secondary prompt string, by default ``> ''.
              PS3    Selection prompt string used within a select loop, by default ``#? ''.
              PS4    The  value of this variable is expanded for parameter evaluation, command substitution,
                     and arithmetic substitution and precedes each line of an execution trace.  By  default,
                     PS4  is  ``+ ''.  In addition when PS4 is unset, the execution trace prompt is also ``+
                     ''.
              SHELL  The pathname of the shell is kept in the environment.  At invocation, if  the  basename
                     of  this  variable  is rsh, rksh, or krsh, then the shell becomes restricted.  If it is
                     pfsh or pfksh, then the shell becomes a profile shell (see pfexec(1)).
              TIMEFORMAT
                     The value of this parameter is used as a format string specifying how the timing infor-mation information
                     mation  for  pipelines prefixed with the time reserved word should be displayed.  The %
                     character introduces a format sequence that is expanded to a time value or other infor-mation. information.
                     mation.  The format sequences and their meanings are as follows.
                     %%        A literal %.
                     %[p][l]R  The elapsed time in seconds.
                     %[p][l]U  The number of CPU seconds spent in user mode.
                     %[p][l]S  The number of CPU seconds spent in system mode.
                     %P        The CPU percentage, computed as (U + S) / R.

                     The brackets denote optional portions.  The optional p is a digit specifying the preci-sion, precision,
                     sion, the number of fractional digits after a decimal point.  A value of  0  causes  no
                     decimal  point  or fraction to be output.  At most three places after the decimal point
                     can be displayed; values of p greater than 3 are treated as 3.  If p is not  specified,
                     the value 3 is used.

                     The  optional  l  specifies a longer format, including hours if greater than zero, min-utes, minutes,
                     utes, and seconds of the form HHhMMmSS.FFs.  The value of p determines whether  or  not
                     the fraction is included.

                     All  other  characters  are  output without change and a trailing newline is added.  If
                     unset, the default value, $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS', is used.  If the  value
                     is null, no timing information is displayed.

              TMOUT  If  set  to  a value greater than zero, TMOUT will be the default timeout value for the
                     read built-in command.  The select compound command terminates after TMOUT seconds when
                     input is from a terminal.  Otherwise, the shell will terminate if a line is not entered
                     within the prescribed number of seconds while reading from a terminal.  (Note that  the
                     shell can be compiled with a maximum bound for this value which cannot be exceeded.)

              VISUAL If  the  value of this variable matches the pattern *[Vv][Ii]*, then the vi option (see
                     Special Command set below) is turned on.  If the value matches the  pattern  *gmacs*  ,
                     the gmacs option is turned on.  If the value matches the pattern *macs*, then the emacs
                     option will be turned on.  The value of VISUAL overrides the value of EDITOR.

       The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK, FCEDIT, TMOUT and  IFS,  while
       HOME,  SHELL,  ENV,  and MAIL are not set at all by the shell (although HOME is set by login(1)).  On
       some systems MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of substitutions are scanned for  the
       field  separator characters (those found in IFS) and split into distinct fields where such characters
       are found.  Explicit null fields ("" or '') are retained.  Implicit null fields (those resulting from
       parameters that have no values or command substitutions with no output) are removed.

       If  the  braceexpand (-B) option is set then each of the fields resulting from IFS are checked to see
       if they contain one or more of the brace patterns {*,*},  {l1..l2}  ,  {n1..n2}  ,  {n1..n2%  fmt}  ,
       {n1..n2  ..n3}  ,  or  {n1..n2  ..n3%fmt}  ,  where * represents any character, l1,l2 are letters and
       n1,n2,n3 are signed numbers and fmt is a format specified as used by printf.  In  each  case,  fields
       are  created  by  prepending  the characters before the { and appending the characters after the } to
       each of the strings generated by the characters between the  {  and  }.   The  resulting  fields  are
       checked to see if they have any brace patterns.

       In the first form, a field is created for each string between { and ,, between , and ,, and between ,
       and }.  The string represented by * can contain embedded matching { and }  without  quoting.   Other-wise, Otherwise,
       wise, each { and } with * must be quoted.

       In the seconds form, l1 and l2 must both be either upper case or both be lower case characters in the
       C locale.  In this case a field is created for each character from l1 thru l2.

       In the remaining forms, a field is created for each number starting at n1  and  continuing  until  it
       reaches  n2  incrementing  n1  by n3.  The cases where n3 is not specified behave as if n3 where 1 if
       n1<=n2 and -1 otherwise.  If forms which specify %fmt any format flags, widths and precisions can  be
       specified  and  fmt can end in any of the specifiers cdiouxX.  For example, {a,z}{1..5..3%02d}{b..c}x
       expands to the 8 fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following splitting, each field is scanned for the characters *, ?, (, and [ unless the -f option has
       been  set.   If  one  of these characters appears, then the word is regarded as a pattern.  Each file
       name component that contains any pattern character is replaced with a lexicographically sorted set of
       names  that  matches the pattern from that directory.  If no file name is found that matches the pat-
       tern, then that component of the filename is left unchanged unless the pattern is prefixed with  ~(N)
       in  which  case  it  is removed as described below.  If FIGNORE is set, then each file name component
       that matches the pattern defined by the value of FIGNORE is  ignored  when  generating  the  matching
       filenames.   The  names  .  and ..  are also ignored.  If FIGNORE is not set, the character .  at the
       start of each file name component will be ignored unless the first character of  the  pattern  corre-sponding corresponding
       sponding to this component is the character .  itself.  Note, that for other uses of pattern matching
       the / and .  are not treated specially.

              *      Matches any string, including the null string.  When used for  filename  expansion,  if
                     the  globstar option is on, two adjacent *'s by itself will match all files and zero or
                     more directories and subdirectories.  If followed by a / then only directories and sub-directories subdirectories
                     directories will match.
              ?      Matches any single character.
              [...]  Matches  any  one  of  the  enclosed  characters.   A pair of characters separated by -matches bymatches
                     matches any character lexically between the pair, inclusive.  If  the  first  character
                     following  the  opening [ is a !  or ^ then any character not enclosed is matched.  A -can Acan
                     can be included in the character set by putting it as the first or last character.
                     Within [ and ], character classes can be specified  with  the  syntax  [:class:]  where
                     class  is  one of the following classes defined in the ANSI-C standard: (Note that word
                     is equivalent to alnum plus the character _.)
                     alnum alpha blank cntrl digit graph lower print punct space upper word xdigit
                     Within [ and ], an equivalence class can be  specified  with  the  syntax  [=c=]  which
                     matches  all  characters with the same primary collation weight (as defined by the cur-rent current
                     rent locale) as the character c.  Within [ and ],  [.symbol.]   matches  the  collating
                     symbol symbol.
       A pattern-list is a list of one or more patterns separated from each other with a & or |.  A & signi-fies signifies
       fies that all patterns must be matched whereas | requires that only one pattern be matched.   Compos-ite Composite
       ite patterns can be formed with one or more of the following sub-patterns:
              ?(pattern-list)
                     Optionally matches any one of the given patterns.
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns.
              +(pattern-list)
                     Matches one or more occurrences of the given patterns.
              {n}(pattern-list)
                     Matches n occurrences of the given patterns.
              {m,n}(pattern-list)
                     Matches  from  m  to  n  occurrences of the given patterns.  If m is omitted, 0 will be
                     used.  If n is omitted at least m occurrences will be matched.
              @(pattern-list)
                     Matches exactly one of the given patterns.
              !(pattern-list)
                     Matches anything except one of the given patterns.
       By default, each pattern, or sub-pattern will match the longest string possible consistent with  gen-erating generating
       erating  the  longest overall match.  If more than one match is possible, the one starting closest to
       the beginning of the string will be chosen.   However, for each of the above compound  patterns  a  -can acan
       can  be  inserted  in  front of the ( to cause the shortest match to the specified pattern-list to be
       used.

       When pattern-list is contained within parentheses, the backslash character  \  is  treated  specially
       even when inside a character class.   All ANSI-C character escapes are recognized and match the spec-ified specified
       ified character.  In addition the following escape sequences are recognized:
              \d     Matches any character in the digit class.
              \D     Matches any character not in the digit class.
              \s     Matches any character in the space class.
              \S     Matches any character not in the space class.
              \w     Matches any character in the word class.
              \W     Matches any character not in the word class.

       A pattern of the form %(pattern-pair(s)) is a sub-pattern that can be used to match nested  character
       expressions.   Each  pattern-pair is a two character sequence which cannot contain & or |.  The first
       pattern-pair specifies the starting and ending characters for the match.   Each  subsequent  pattern-pair patternpair
       pair  represents the beginning and ending characters of a nested group that will be skipped over when
       counting starting and ending character matches.  The behavior is unspecified when the first character
       of a pattern-pair is alpha-numeric except for the following:
              D      Causes  the ending character to terminate the search for this pattern without finding a
                     match.
              E      Causes the ending character to be interpreted as an escape character.
              L      Causes the ending character to be interpreted as a quote character causing all  charac-ters characters
                     ters to be ignored when looking for a match.
              Q      Causes  the ending character to be interpreted as a quote character causing all charac-ters characters
                     ters other than any escape character to be ignored when looking for a match.
       Thus, %({}Q"E\), matches characters starting at { until the matching } is found not counting any { or
       }  that  is inside a double quoted string or preceded by the escape character \.  Without the {} this
       pattern matches any C language string.

       Each sub-pattern in a composite pattern is numbered, starting at 1, by the location of the  (  within
       the  pattern.   The  sequence \n, where n is a single digit and \n comes after the n-th. sub-pattern,
       matches the same string as the sub-pattern itself.

       Finally a pattern can contain sub-patterns of the form ~(options:pattern-list), where either  options
       or  :pattern-list  can  be  omitted.   Unlike the other compound patterns, these sub-patterns are not
       counted in the numbered sub-patterns.  :pattern-list must  be  omitted  for  the  upper-case  options
       below.  If options is present, it can consist of one or more of the following:
              +      Enable the following options.  This is the default.
              -      Disable the following options.
              E      The  remainder of the pattern uses extended regular expression syntax like the egrep(1)
                     command.
              F      The remainder of the pattern uses fgrep(1) expression syntax.
              G      The remainder of the pattern uses basic regular expression syntax like the grep(1) com-mand. command.
                     mand.
              K      The remainder of the pattern uses shell pattern syntax.  This is the default.
              N      This  is ignored.  However, when it is the first letter and is used with file name gen-eration, generation,
                     eration, and no matches occur, the file pattern expands to the empty string.
              X      The remainder of the pattern uses augmented regular expression syntax like the xgrep(1)
                     command.
              i      Treat the match as case insensitive.
              g      File the longest match (greedy).  This is the default.
              l      Left anchor the pattern.  This is the default for K style patterns.
              r      Right anchor the pattern.  This is the default for K style patterns.
       If  both options and :pattern-list are specified, then the options apply only to  pattern-list.  Oth-erwise, Otherwise,
       erwise, these options remain in effect until they are disabled by a subsequent ~(...) or at  the  end
       of the sub-pattern containing ~(...).

   Quoting.
       Each  of the metacharacters listed earlier (see Definitions above) has a special meaning to the shell
       and causes termination of a word unless quoted.  A character may be quoted (i.e., made to  stand  for
       itself)  by preceding it with a \.  The pair \new-line is removed.  All characters enclosed between a
       pair of single quote marks ('') that is not preceded by a $ are quoted.  A single quote cannot appear
       within the single quotes.  A single quoted string preceded by an unquoted $ is processed as an ANSI-C
       string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
              Expands to the collating element name.

       Inside double quote marks (""), parameter and command substitution occur and \ quotes the  characters
       \, `, ", and $.  A $ in front of a double quoted string will be ignored in the "C" or "POSIX" locale,
       and may cause the string to be replaced by a locale specific string otherwise.  The meaning of $* and
       $@  is identical when not quoted or when used as a variable assignment value or as a file name.  How-ever, However,
       ever, when used as a command argument, "$*" is equivalent to "$1d$2d...", where d is the first  char-acter character
       acter  of  the  IFS  variable, whereas "$@" is equivalent to "$1" "$2" ....  Inside grave quote marks
       (``), \ quotes the characters \, `, and $.  If the grave quotes occur within double  quotes,  then  \
       also quotes the character ".

       The  special  meaning  of  reserved  words  or aliases can be removed by quoting any character of the
       reserved word.  The recognition of function names or built-in command names listed  below  cannot  be
       altered by quoting them.

   Arithmetic Evaluation.
       The  shell performs arithmetic evaluation for arithmetic substitution, to evaluate an arithmetic com-mand, command,
       mand, to evaluate an indexed array subscript, and to evaluate  arguments  to  the  built-in  commands
       shift  and  let.   Evaluations are performed using double precision floating point arithmetic or long
       double precision floating point for systems that provide this data type.   Floating  point  constants
       follow  the  ANSI-C  programming  language  floating point conventions.  Integer constants follow the
       ANSI-C programming language integer constant conventions although only  single  byte  character  con-stants constants
       stants  are  recognized  and character casts are not recognized.  In addition constants can be of the
       form [base#]n where base is a decimal number between two and sixty-four representing  the  arithmetic
       base  and  n is a number in that base.  The digits above 9 are represented by the lower case letters,
       the upper case letters, @, and _ respectively.  For bases less than or equal to 36, upper  and  lower
       case characters can be used interchangeably.

       An  arithmetic  expression uses the same syntax, precedence, and associativity of expression as the C
       language.  All the C language operators that apply to floating point  quantities  can  be  used.   In
       addition,  the operator ** can be used for exponentiation.  It has higher precedence than multiplica-tion multiplication
       tion and is left associative.  In addition, when the value of an arithmetic variable  or  sub-expres-sion sub-expression
       sion  can  be represented as a long integer, all C language integer arithmetic operations can be per-formed. performed.
       formed.  Variables can be referenced by name within an arithmetic expression without using the param-eter parameter
       eter  expansion  syntax.   When  a  variable  is  referenced, its value is evaluated as an arithmetic
       expression.

       Any of the following math library functions that are in the C math library  can  be  used  within  an
       arithmetic expression:

       abs  acos  acosh asin asinh atan atan2 atanh cbrt copysign cos cosh erf erfc exp exp2 expm1 fabs fdim
       finite floor fma fmax fmin fmod hypot ilogb int isinf isnan j0 j1 jn lgamma log log2  logb  nearbyint
       nextafter  nexttoward  pow remainder rint round sin sinh sqrt tan tanh tgamma trunc y0 y1 yn In addi-tion, addition,
       tion, arithmetic functions can be define as shell functions with a variant of the function name  syn-tax, syntax,
       tax,

       function .sh.math.name ident ... { list ;}
              where  name  is the function name used in the arithmetic expression and each identifier, ident
              is a name reference to the long double precission  floating  point  argument.   The  value  of
              .sh.value when the function returns is the value of this function.  User defined functions can
              take up to 3 arguments and override C math library functions.

       An internal representation of a variable as a double precision floating point can be  specified  with
       the  -E  [n], -F [n], or -X [n] option of the typeset special built-in command.  The -E option causes
       the expansion of the value to be represented using scientific notation  when  it  is  expanded.   The
       optional  option  argument  n  defines  the  number of significant figures.  The -F option causes the
       expansion to be represented as a floating decimal number when it is expanded.  The  -X  option  cause
       the  expansion  to be represented using the %a format defined by ISO C-99.  The optional option argu-ment argument
       ment n defines the number of places after the decimal (or radix) point in this case.

       An internal integer representation of a variable can be specified with the -i [n] option of the type-set typeset
       set special built-in command.  The optional option argument n specifies an arithmetic base to be used
       when expanding the variable.  If you do not specify an arithmetic base, base 10 will be used.

       Arithmetic evaluation is performed on the value of each assignment to a variable with the -E, -F, -X,
       or -i attribute.  Assigning a floating point number to a variable whose type is an integer causes the
       fractional part to be truncated.


   Prompting.
       When used interactively, the shell prompts with the value of PS1 after  expanding  it  for  parameter
       expansion, command substitution, and arithmetic substitution, before reading a command.  In addition,
       each single !  in the prompt is replaced by the command number.  A !!  is required to place !  in the
       prompt.   If  at any time a new-line is typed and further input is needed to complete a command, then
       the secondary prompt (i.e., the value of PS2) is issued.

   Conditional Expressions.
       A conditional expression is used with the [[ compound command to test attributes of files and to com-pare compare
       pare strings.  Field splitting and file name generation are not performed on the words between [[ and
       ]].  Each expression can be constructed from one or more of the following  unary  or  binary  expres-sions: expressions:
       sions:
       string True, if string is not null.
       -a file
              Same as -e below.  This is obsolete.
       -b file
              True, if file exists and is a block special file.
       -c file
              True, if file exists and is a character special file.
       -d file
              True, if file exists and is a directory.
       -e file
              True, if file exists.
       -f file
              True, if file exists and is an ordinary file.
       -g file
              True, if file exists and it has its setgid bit set.
       -k file
              True, if file exists and it has its sticky bit set.
       -n string
              True, if length of string is non-zero.
       -o ?option
              True, if option named option is a valid option name.
       -o option
              True, if option named option is on.
       -p file
              True, if file exists and is a fifo special file or a pipe.
       -r file
              True, if file exists and is readable by current process.
       -s file
              True, if file exists and has size greater than zero.
       -t fildes
              True, if file descriptor number fildes is open and associated with a terminal device.
       -u file
              True, if file exists and it has its setuid bit set.
       -w file
              True, if file exists and is writable by current process.
       -x file
              True, if file exists and is executable by current process.  If file exists and is a directory,
              then true if the current process has permission to search in the directory.
       -z string
              True, if length of string is zero.
       -L file
              True, if file exists and is a symbolic link.
       -h file
              True, if file exists and is a symbolic link.
       -N file
              True, if file exists and the modification time is greater than the last access time.
       -O file
              True, if file exists and is owned by the effective user id of this process.
       -G file
              True, if file exists and its group matches the effective group id of this process.
       -S file
              True, if file exists and is a socket.
       file1 -nt file2
              True, if file1 exists and file2 does not, or file1 is newer than file2.
       file1 -ot file2
              True, if file2 exists and file1 does not, or file1 is older than file2.
       file1 -ef file2
              True, if file1 and file2 exist and refer to the same file.
       string == pattern
              True, if string matches pattern.  Any part of pattern can be quoted to cause it to be  matched
              as  a string.  With a successful match to a pattern, the .sh.match array variable will contain
              the match and sub-pattern matches.
       string = pattern
              Same as == above, but is obsolete.
       string != pattern
              True, if string does not match pattern.  When the string matches  the  pattern  the  .sh.match
              array variable will contain the match and sub-pattern matches.
       string =~ ere
              True if string matches the pattern ~(E)ere where ere is an extended regular expression.
       string1 < string2
              True, if string1 comes before string2 based on ASCII value of their characters.
       string1 > string2
              True, if string1 comes after string2 based on ASCII value of their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
              True, if exp1 is equal to exp2.
       exp1 -ne exp2
              True, if exp1 is not equal to exp2.
       exp1 -lt exp2
              True, if exp1 is less than exp2.
       exp1 -gt exp2
              True, if exp1 is greater than exp2.
       exp1 -le exp2
              True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
              True, if exp1 is greater than or equal to exp2.

       In  each  of the above expressions, if file is of the form /dev/fd/n, where n is an integer, then the
       test is applied to the open file whose descriptor number is n.

       A compound expression can be constructed from these primitives by using any of the following,  listed
       in decreasing order of precedence.
       (expression)
              True, if expression is true.  Used to group expressions.
       ! expression
              True if expression is false.
       expression1 && expression2
              True, if expression1 and expression2 are both true.
       expression1 || expression2
              True, if either expression1 or expression2 is true.

   Input/Output.
       Before  a command is executed, its input and output may be redirected using a special notation inter-preted interpreted
       preted by the shell.  The following may appear anywhere in a simple-command or may precede or  follow
       a  command  and are not passed on to the invoked command.  Command substitution, parameter expansion,
       and arithmetic substitution occur before word or digit is used except as noted below.  File name gen-eration generation
       eration  occurs only if the shell is interactive and the pattern matches a single file.  Field split-ting splitting
       ting is not performed.

       In  each  of  the  following  redirections,   if   file   is   of   the   form   /dev/sctp/host/port,
       /dev/tcp/host/port,  or  /dev/udp/host/port,  where host is a hostname or host address, and port is a
       service given by name or an integer port number, then the redirection attempts to make a tcp, sctp or
       udp connection to the corresponding socket.

       No intervening space is allowed between the characters of redirection operators.

       <word         Use file word as standard input (file descriptor 0).

       >word         Use  file word as standard output (file descriptor 1).  If the file does not exist then
                     it is created.  If the file exists, and the noclobber option  is  on,  this  causes  an
                     error; otherwise, it is truncated to zero length.

       >|word        Sames as >, except that it overrides the noclobber option.

       >;word        Write  output  to a temporary file.  If the command completes successfully rename it to
                     word, otherwise, delete the temporary file.  >;word cannot be used  with  the  exec(2).
                     built-in.

       >>word        Use  file  word  as standard output.  If the file exists, then output is appended to it
                     (by first seeking to the end-of-file); otherwise, the file is created.

       <>word        Open file word for reading and writing as standard output.

       <>;word       The same as <>word except that if the command completes successfully, word is truncated
                     to  the offset at command completion.  <>;word cannot be used with the exec(2).  built-in. builtin.
                     in.

       <<[-]word     The shell input is read up to a line that is the same as word  after  any  quoting  has
                     been  removed,  or to an end-of-file.  No parameter substitution, command substitution,
                     arithmetic substitution or file name generation is performed on  word.   The  resulting
                     document, called a here-document, becomes the standard input.  If any character of word
                     is quoted, then no interpretation is placed upon the characters of the document; other-
                     wise,  parameter  expansion,  command  substitution, and arithmetic substitution occur,
                     \new-line is ignored, and \ must be used to quote the characters \,  $,  `.   If  -  is
                     appended to <<, then all leading tabs are stripped from word and from the document.  If
                     # is appended to <<, then leading spaces and tabs will be stripped off the  first  line
                     of the document and up to an equivalent indentation will be stripped from the remaining
                     lines and from word.  A tab stop is assumed to occur at every 8 columns  for  the  pur-
                     poses of determining the indentation.

       <<<word       A  short  form of here document in which word becomes the contents of the here-document
                     after any parameter expansion, command substitution, and arithmetic substitution occur.

       <&digit       The  standard  input  is duplicated from file descriptor digit (see dup(2)).  Similarly
                     for the standard output using >&digit.

       <&digit-      The file descriptor given by digit is moved to standard input.  Similarly for the stan-
                     dard output using >&digit-.

       <&-           The standard input is closed.  Similarly for the standard output using >&-.

       <&p           The input from the co-process is moved to standard input.

       >&p           The output to the co-process is moved to standard output.

       <#((expr))    Evaluate  arithmetic  expression  expr  and position file descriptor 0 to the resulting
                     value bytes from the start of the file.  The variables CUR and EOF evaluate to the cur-
                     rent offset and end-of-file offset respectively when evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks forward to the beginning of the next line containing pattern.

       <##pattern    The  same  as <# except that the portion of the file that is skipped is copied to stan-
                     dard output.

       If one of the above is preceded by a digit, with no intervening space, then the file descriptor  num-ber number
       ber referred to is that specified by the digit (instead of the default 0 or 1).  If one of the above,
       other than >&- and the ># and <# forms, is preceded by {varname} with no intervening  space,  then  a
       file descriptor number > 10 will be selected by the shell and stored in the variable varname.  If >&-or >&or
       or the any of the ># and <# forms is preceded by {varname} the value  of  varname  defines  the  file
       descriptor to close or position.  For example:

              ... 2>&1

       means file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1 and

              exec {n}<file

       means open file named file for reading and store the file descriptor number in variable n.

       The  order  in which redirections are specified is significant.  The shell evaluates each redirection
       in terms of the (file descriptor, file) association at the time of evaluation.  For example:

              ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates file descriptor  2  with  the
       file  associated  with  file descriptor 1 (i.e.  fname).  If the order of redirections were reversed,
       file descriptor 2 would be associated with the terminal (assuming file descriptor  1  had  been)  and
       then file descriptor 1 would be associated with file fname.

       If  a command is followed by & and job control is not active, then the default standard input for the
       command is the empty file /dev/null.  Otherwise, the environment for the execution of a command  con-tains contains
       tains the file descriptors of the invoking shell as modified by input/output specifications.

   Environment.
       The  environment (see environ(7)) is a list of name-value pairs that is passed to an executed program
       in the same way as a normal argument list.  The names must be identifiers and the values are  charac-ter character
       ter  strings.   The  shell  interacts with the environment in several ways.  On invocation, the shell
       scans the environment and creates a variable for each name found, giving it the  corresponding  value
       and  attributes and marking it export.  Executed commands inherit the environment.  If the user modi-fies modifies
       fies the values of these variables or creates new ones, using the export or typeset -x commands, they
       become part of the environment.  The environment seen by any executed command is thus composed of any
       name-value pairs originally inherited by the shell, whose values  may  be  modified  by  the  current
       shell, plus any additions which must be noted in export or typeset -x commands.

       The  environment for any simple-command or function may be augmented by prefixing it with one or more
       variable assignments.  A variable assignment argument is a word of the form identifier=value.  Thus:

              TERM=450 cmd args                  and
              (export TERM; TERM=450; cmd args)

       are equivalent (as far as the above execution of cmd is concerned except for  special  built-in  com-mands commands
       mands listed below - those that are preceded with a dagger).

       If  the  obsolete  -k option is set, all variable assignment arguments are placed in the environment,
       even if they occur after the command name.  The following first prints a=b c and then c:

              echo a=b c
              set -k
              echo a=b c
       This feature is intended for use with scripts written for early versions of the shell and its use  in
       new scripts is strongly discouraged.  It is likely to disappear someday.

   Functions.
       For  historical  reasons,  there are two ways to define functions, the name() syntax and the function
       name syntax, described in the Commands section above.  Shell functions are read in and stored  inter-nally. internally.
       nally.   Alias  names  are  resolved when the function is read.  Functions are executed like commands
       with the arguments passed as positional parameters.  (See Execution below.)

       Functions defined by the function name syntax and called by name execute in the same process  as  the
       caller and share all files and present working directory with the caller.  Traps caught by the caller
       are reset to their default action inside the function.  A  trap  condition  that  is  not  caught  or
       ignored  by  the  function  causes the function to terminate and the condition to be passed on to the
       caller.  A trap on EXIT set inside a function is executed in the environment of the caller after  the
       function  completes.   Ordinarily, variables are shared between the calling program and the function.
       However, the typeset special built-in command used within a function defines  local  variables  whose
       scope  includes the current function.  They can be passed to functions that they call in the variable
       assignment list that precedes the call or as arguments passed  as  name  references.   Errors  within
       functions return control to the caller.

       Functions defined with the name() syntax and functions defined with the function name syntax that are
       invoked with the .  special built-in are executed in the caller's environment and share all variables
       and  traps  with  the caller.  Errors within these function executions cause the script that contains
       them to abort.

       The special built-in command return is used to return from function calls.

       Function names can be listed with the -f or +f option of the typeset special built-in  command.   The
       text  of functions, when available, will also be listed with -f.  Functions can be undefined with the
       -f option of the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.  Functions that  need  to  be
       defined  across separate invocations of the shell should be placed in a directory and the FPATH vari-able variable
       able should contain the name of this directory.  They may also be specified in the ENV file.

   Discipline Functions.
       Each variable can have zero or more discipline functions associated with  it.   The  shell  initially
       understands  the  discipline  names  get,  set,  append, and unset but can be added when defining new
       types.  On most systems others can be added at run time via the  C  programming  interface  extension
       provided  by  the  builtin  built-in utility.  If the get discipline is defined for a variable, it is
       invoked whenever the given variable is referenced.  If the variable .sh.value  is  assigned  a  value
       inside  the discipline function, the referenced variable will evaluate to this value instead.  If the
       set discipline is defined for a variable, it is invoked whenever the given  variable  is  assigned  a
       value.   If  the  append  discipline  is  defined  for  a variable, it is invoked whenever a value is
       appended to the given variable.  The variable .sh.value is given the value  of  the  variable  before
       invoking  the  discipline,  and the variable will be assigned the value of .sh.value after the disci-pline discipline
       pline completes.  If .sh.value is unset inside the discipline, then that value is unchanged.  If  the
       unset  discipline is defined for a variable, it is invoked whenever the given variable is unset.  The
       variable will not be unset unless it is unset explicitly from within this discipline function.

       The variable .sh.name contains the name of the variable for which the discipline function is  called,
       .sh.subscript  is  the subscript of the variable, and .sh.value will contain the value being assigned
       inside the set discipline function.  The variable _ is a reference to the variable including the sub-script subscript
       script  if any.  For the set discipline, changing .sh.value will change the value that gets assigned.
       Finally, the expansion ${var.name}, when name is the name of a discipline, and there is  no  variable
       of this name, is equivalent to the command substitution ${ var.name;}.


   Name Spaces.
       Commands and functions that are executed as part of the list of a namespace command that modify vari-ables variables
       ables or create new ones, create a new variable whose name is the name of the name space as given  by
       identifier preceded by ..  When a variable whose name is name is referenced, it is first searched for
       using .identifier.name.  Similarly, a function defined by a command in the namespace list is  created
       using the name space name  preceded by a ..

       When   the  list of a namespace command contains a namespace command, the names of variable and func-tions functions
       tions that are created consist of the variable or function name preceded by the list  of  identifiers
       each preceded by ..

       Outside  of  a  name  space, a variable or function created inside a names space can be referenced by
       preceding it with the name space name.

       By default, variables staring with .sh are in the sh name space.


   Type Variables.
       Typed variables provide a way to create data structure and objects.  A type can be defined either  by
       a  shared library, by the enum built-in command described below, or by using the new -T option of the
       typeset built-in command.  With the -T option of typeset, the type name, specified as an option argu-ment argument
       ment  to  -T, is set with a compound variable assignment that defines the type.  Function definitions
       can appear inside the compound variable assignment and these become  discipline  functions  for  this
       type  and  can  be  invoked  or  redefined by each instance of the type.  The function name create is
       treated specially.  It is invoked for each instance of the type that is created but is not  inherited
       and cannot be redefined for each instance.

       When  a type is defined a special built-in command of that name is added.  These built-ins are decla-ration declaration
       ration commands and follow the same expansion rules as all  the  special  built-in  commands  defined
       below  that  are preceded by ||.  These commands can subsequently be used inside further type defini-tions. definitions.
       tions.  The man page for these commands can be generated by using the --man  option  or  any  of  the
       other -- options described with getopts.  The -r, -a, -A, -h, and -S options of typeset are permitted
       with each of these new built-ins.

       An instance of a type is created by invoking the type name followed by one or  more  instance  names.
       Each  instance  of  the type is initialized with a copy of the sub-variables except for sub-variables
       that are defined with the -S option.  Variables defined with the -S are shared by  all  instances  of
       the  type.  Each instance can change the value of any sub-variable and can also define new discipline
       functions of the same names as those defined by the type definition as well as  any  standard  disci-pline discipline
       pline names.  No additional sub-variables can be defined for any instance.

       When defining a type, if the value of a sub-variable is not set and the -r attribute is specified, it
       causes the sub-variable to be a required sub-variable.  Whenever an instance of a  type  is  created,
       all  required sub-variables must be specified.  These sub-variables become readonly in each instance.

       When unset is invoked on a sub-variable within a type, and the -r attribute has  not  been  specified
       for this field, the value is reset to the default value associative with the type.  Invoking unset on
       a type instance not contained within another type deletes all sub-variables and the variable  itself.

       A type definition can be derived from another type definition by defining the first sub-variable name
       as _ and defining its type as the base type.  Any remaining definitions will be additions and modifi-cations modifications
       cations  that  apply to the new type.  If the new type name is the same is that of the base type, the
       type will be replaced and the original type will no longer be accessible.

       The typeset command with the -T and no option argument or operands will write all  the  type  defini-tions definitions
       tions to standard output in a form that that can be read in to create all they types.

   Jobs.
       If  the  monitor  option  of the set command is turned on, an interactive shell associates a job with
       each pipeline.  It keeps a table of current jobs, printed by the jobs command, and assigns them small
       integer  numbers.   When  a job is started asynchronously with &, the shell prints a line which looks
       like:

            [1] 1234

       indicating that the job which was started asynchronously was job number 1  and  had  one  (top-level)
       process, whose process id was 1234.

       This  paragraph and the next require features that are not in all versions of UNIX and may not apply.
       If you are running a job and wish to do something else you may hit the key ^Z (control-Z) which sends
       a  STOP  signal  to  the  current  job.   The shell will then normally indicate that the job has been
       `Stopped', and print another prompt.  You can then manipulate the state of this job,  putting  it  in
       the background with the bg command, or run some other commands and then eventually bring the job back
       into the foreground with the foreground command fg.  A ^Z takes effect immediately  and  is  like  an
       interrupt in that pending output and unread input are discarded when it is typed.

       A  job  being run in the background will stop if it tries to read from the terminal.  Background jobs
       are normally allowed to produce output, but this can be disabled by giving the command  stty  tostop.
       If  you set this tty option, then background jobs will stop when they try to produce output like they
       do when they try to read input.

       A job pool is a collection of jobs started with list & associated with a name.

       There are several ways to refer to jobs in the shell.  A job can be referred to by the process id  of
       any process of the job or by one of the following:
       %number
              The job with the given number.
       pool   All the jobs in the job pool named by pool.
       pool.number
              The job number number in the job pool named by pool.
       %string
              Any job whose command line begins with string.
       %?string
              Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous  job.  In addition, unless noted otherwise, wherever a job can be specified, the name
              of a background job pool can be used to represet all the jobs in that pool.

       The shell learns immediately whenever a process changes state.  It normally informs  you  whenever  a
       job becomes blocked so that no further progress is possible, but only just before it prints a prompt.
       This is done so that it does not otherwise disturb your work.  The notify option of the  set  command
       causes the shell to print these job change messages as soon as they occur.

       When the monitor option is on, each background job that completes triggers any trap set for CHLD.

       When  you try to leave the shell while jobs are running or stopped, you will be warned that `You have
       stopped(running) jobs.'  You may use the jobs command to see what they are.  If you  immediately  try
       to  exit  again,  the shell will not warn you a second time, and the stopped jobs will be terminated.
       When a login shell receives a HUP signal, it sends a HUP signal to each job that has  not  been  dis-owned disowned
       owned with the disown built-in command described below.

   Signals.
       The  INT  and QUIT signals for an invoked command are ignored if the command is followed by & and the
       monitor option is not active.  Otherwise, signals have the values inherited by  the  shell  from  its
       parent (but see also the trap built-in command below).

   Execution.
       Each  time  a  command is read, the above substitutions are carried out.  If the command name matches
       one of the Special Built-in Commands listed below, it is executed within the current  shell  process.
       Next,  the  command  name  is  checked to see if it matches a user defined function.  If it does, the
       positional parameters are saved and then reset to the arguments of the function call.  A function  is
       also  executed  in  the  current  shell process.  When the function completes or issues a return, the
       positional parameter list is restored.  For functions defined with the function name syntax, any trap
       set  on  EXIT within the function is executed.  The exit value of a function is the value of the last
       command executed.  If a command name is not a special built-in command or a  user  defined  function,
       but it is one of the built-in commands listed below, it is executed in the current shell process.

       The  shell  variable PATH defines the search path for the directory containing the command.  Alterna-tive Alternative
       tive directory names are separated by a colon (:).  The default path  is  /bin:/usr/bin:  (specifying
       /bin,  /usr/bin, and the current directory in that order).  The current directory can be specified by
       two or more adjacent colons, or by a colon at the beginning or end of the path list.  If the  command
       name  contains  a  /,  then  the  search  path is not used.  Otherwise, each directory in the path is
       searched for an executable file of the given name that is not a directory.   If  found,  and  if  the
       shell  determines  that  there  is a built-in version of a command corresponding to a given pathname,
       this built-in is invoked in the current process.  If found, and this directory is also  contained  in
       the value of the FPATH variable, then this file is loaded into the current shell environment as if it
       were the argument to the . command except that only preset aliases are expanded, and  a  function  of
       the  given name is executed as described above.  If not found, and the file .paths is found, and this
       file contains a line of the form FPATH=path where path names an existing directory, and  this  direc-tory directory
       tory  contains  a file of the given name, then this file is loaded into the current shell environment
       as if it were the argument to the . special built-in command and a function of the given name is exe-cuted. executed.
       cuted.   Otherwise,  if found, a process is created and an attempt is made to execute the command via
       exec(2).

       When an executable is found, the directory where it is found in is searched for a file named  .paths.
       If  this  file is found and it contains a line of the form BUILTIN_LIB=value , then the library named
       by value will be searched for as if it were an option argument to builtin -f, and if  it  contains  a
       built-in  of  the specified name this will be executed instead of a command by this name.  Otherwise,
       if this file is found and it contains a line of the form name=value in the first or second line, then
       the  environment  variable  name  is  modified  by prepending the directory specified by value to the
       directory list.  If value is not an absolute directory, then it specifies a directory relative to the
       directory  that the executable was found.  If the environment variable name does not already exist it
       will be added to the environment list for the specified command.

       If the file has execute permission but is not an a.out file, it is assumed to be  a  file  containing
       shell  commands.   A separate shell is spawned to read it.  All non-exported variables are removed in
       this case.  If the shell command file doesn't have read permission, or if the  setuid  and/or  setgid
       bits  are set on the file, then the shell executes an agent whose job it is to set up the permissions
       and execute the shell with the shell command file passed down as an open file.  A parenthesized  com-mand command
       mand is executed in a sub-shell without removing non-exported variables.

   Command Re-entry.
       The  text  of  the  last HISTSIZE (default 512) commands entered from a terminal device is saved in a
       history file.  The file $HOME/.sh_history is used if the HISTFILE variable is not set or if the  file
       it  names  is  not writable.  A shell can access the commands of all interactive shells which use the
       same named HISTFILE.  The built-in command hist is used to list or edit a portion of this file.   The
       portion of the file to be edited or listed can be selected by number or by giving the first character
       or characters of the command.  A single command or range of commands can be specified.  If you do not
       specify an editor program as an argument to hist then the value of the variable HISTEDIT is used.  If
       HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT is not defined, then  /bin/ed  is
       used.  The edited command(s) is printed and re-executed upon leaving the editor unless you quit with-out without
       out writing.  The -s option (and in obsolete versions, the editor name -) is used to skip the editing
       phase  and  to re-execute the command.  In this case a substitution parameter of the form old=new can
       be used to modify the command before execution.  For example, with  the  preset  alias  r,  which  is
       aliased to 'hist -s', typing `r bad=good c' will re-execute the most recent command which starts with
       the letter c, replacing the first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally, each command line entered from a terminal device is simply typed  followed  by  a  new-line
       (`RETURN' or `LINE FEED').  If either the emacs, gmacs, or vi option is active, the user can edit the
       command line.  To be in either of these edit modes set the corresponding option.  An  editing  option
       is  automatically  selected  each  time  the  VISUAL or EDITOR variable is assigned a value ending in
       either of these option names.

       The editing features require that the user's terminal accept `RETURN' as carriage return without line
       feed and that a space (` ') must overwrite the current character on the screen.

       Unless  the  multiline  option is on, the editing modes implement a concept where the user is looking
       through a window at the current line.  The window width is the value of COLUMNS  if  it  is  defined,
       otherwise 80.  If the window width is too small to display the prompt and leave at least 8 columns to
       enter input, the prompt is truncated from the left.  If the line is  longer  than  the  window  width
       minus  two, a mark is displayed at the end of the window to notify the user.  As the cursor moves and
       reaches the window boundaries the window will be centered about the cursor.  The mark is a >  (<,  *)
       if the line extends on the right (left, both) side(s) of the window.

       The  search commands in each edit mode provide access to the history file.  Only strings are matched,
       not patterns, although a leading ^ in the string restricts the match to begin at the first  character
       in the line.

       Each  of the edit modes has an operation to list the files or commands that match a partially entered
       word.  When applied to the first word on the line, or the first word after a ;, |, &, or (,  and  the
       word  does  not  begin with ~ or contain a /, the list of aliases, functions, and executable commands
       defined by the PATH variable that could match the partial word is displayed.  Otherwise, the list  of
       files  that  match  the  given word is displayed.  If the partially entered word does not contain any
       file expansion characters, a * is appended before generating these lists.  After displaying the  gen-
       erated  list,  the  input line is redrawn.  These operations are called command name listing and file
       name listing, respectively.  There are additional operations, referred to as command name  completion
       and file name completion, which compute the list of matching commands or files, but instead of print-ing printing
       ing the list, replace the current word with a complete or partial match.  For file  name  completion,
       if  the  match  is  unique, a / is appended if the file is a directory and a space is appended if the
       file is not a directory.  Otherwise, the longest common prefix for all the  matching  files  replaces
       the  word.  For command name completion, only the portion of the file names after the last / are used
       to find the longest command prefix.  If only a single name matches this  prefix,  then  the  word  is
       replaced  with  the  command name followed by a space.  When using a tab for completion that does not
       yield a unique match, a subsequent tab will provide a numbered list of matching alternatives.  A spe-cific specific
       cific selection can be made by entering the selection number followed by a tab.

   Key Bindings.
       The  KEYBD  trap  can  be used to intercept keys as they are typed and change the characters that are
       actually seen by the shell.  This trap is executed after each character (or  sequence  of  characters
       when  the  first character is ESC) is entered while reading from a terminal.  The variable .sh.edchar
       contains the character or character sequence  which  generated  the  trap.   Changing  the  value  of
       .sh.edchar  in  the  trap action causes the shell to behave as if the new value were entered from the
       keyboard rather than the original value.

       The variable .sh.edcol is set to the input column number of the cursor at the time of the input.  The
       variable  .sh.edmode  is  set  to  ESC  when in vi insert mode (see below) and is null otherwise.  By
       prepending ${.sh.editmode} to a value assigned to .sh.edchar it will cause the  shell  to  change  to
       control mode if it is not already in this mode.

       This  trap is not invoked for characters entered as arguments to editing directives, or while reading
       input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The only difference between these
       two modes is the way they handle ^T.  To edit, the user moves the cursor to the point needing correc-tion correction
       tion and then inserts or deletes characters or words as needed.  All the editing commands are control
       characters  or  escape  sequences.   The notation for control characters is caret (^) followed by the
       character.  For example, ^F is the notation for control F.  This is entered by depressing  `f'  while
       holding  down  the  `CTRL' (control) key.  The `SHIFT' key is not depressed.  (The notation ^?  indi-cates indicates
       cates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a character.  For example, M-f  (pronounced  Meta
       f) is entered by depressing ESC (ascii 033) followed by `f'.  (M-F would be the notation for ESC fol-lowed followed
       lowed by `SHIFT' (capital) `F'.)

       All edit commands operate from any place on the line  (not  just  at  the  beginning).   Neither  the
       `RETURN' nor the `LINE FEED' key is entered after edit commands except when noted.

       ^F        Move cursor forward (right) one character.
       M-[C      Move cursor forward (right) one character.
       M-f       Move cursor forward one word.  (The emacs editor's idea of a word is a string of characters
                 consisting of only letters, digits and underscores.)
       ^B        Move cursor backward (left) one character.
       M-[D      Move cursor backward (left) one character.
       M-b       Move cursor backward one word.
       ^A        Move cursor to start of line.
       M-[H      Move cursor to start of line.
       ^E        Move cursor to end of line.
       M-[Y      Move cursor to end of line.
       ^]char    Move cursor forward to character char on current line.
       M-^]char  Move cursor backward to character char on current line.
       ^X^X      Interchange the cursor and mark.
       erase     (User defined erase character as defined by the stty(1) command, usually ^H or #.)   Delete
                 previous character.
       lnext     (User  defined  literal  next  character  as  defined  by the stty(1) command, or ^V if not
                 defined.)  Removes the next character's editing features (if any).
       ^D        Delete current character.
       M-d       Delete current word.
       M-^H      (Meta-backspace) Delete previous word.
       M-h       Delete previous word.
       M-^?      (Meta-DEL) Delete previous word (if your interrupt character is ^?  (DEL, the default) then
                 this command will not work).
       ^T        Transpose  current  character with previous character and advance the cursor in emacs mode.
                 Transpose two previous characters in gmacs mode.
       ^C        Capitalize current character.
       M-c       Capitalize current word.
       M-l       Change the current word to lower case.
       ^K        Delete from the cursor to the end of the line.  If preceded by a numerical parameter  whose
                 value  is  less than the current cursor position, then delete from given position up to the
                 cursor.  If preceded by a numerical parameter whose value is greater than the current  cur-sor cursor
                 sor position, then delete from cursor up to given cursor position.
       ^W        Kill from the cursor to the mark.
       M-p       Push the region from the cursor to the mark on the stack.
       kill      (User  defined  kill  character as defined by the stty command, usually ^G or @.)  Kill the
                 entire current line.  If two kill characters are entered in succession, all kill characters
                 from then on cause a line feed (useful when using paper terminals).
       ^Y        Restore last item removed from line. (Yank item back to the line.)
       ^L        Line feed and print current line.
       M-^L      Clear the screen.
       ^@        (Null character) Set mark.
       M-space   (Meta space) Set mark.
       ^J        (New line) Execute the current line.
       ^M        (Return) Execute the current line.
       eof       End-of-file character, normally ^D, is processed as an End-of-file only if the current line
                 is null.
       ^P        Fetch previous command.  Each time ^P is entered the  previous  command  back  in  time  is
                 accessed.  Moves back one line when not on the first line of a multi-line command.
       M-[A      If the cursor is at the end of the line, it is equivalent to ^R with string set to the con-tents contents
                 tents of the current line.  Otherwise, it is equivalent to ^P.
       M-<       Fetch the least recent (oldest) history line.
       M->       Fetch the most recent (youngest) history line.
       ^N        Fetch next command line.  Each time ^N is entered the next command line forward in time  is
                 accessed.
       M-[B      Equivalent to ^N.
       ^Rstring  Reverse  search  history  for a previous command line containing string.  If a parameter of
                 zero is given, the search is forward.  String is terminated by a  `RETURN'  or  `NEW LINE'.
                 If  string is preceded by a ^, the matched line must begin with string.  If string is omit-ted, omitted,
                 ted, then the next command line containing the most recent string  is  accessed.   In  this
                 case a parameter of zero reverses the direction of the search.
       ^O        Operate  -  Execute  the current line and fetch the next line relative to current line from
                 the history file.
       M-digits  (Escape) Define numeric parameter, the digits are taken as a parameter to the next command.
                 The  commands  that  accept a parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
                 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter  Soft-key - Your alias list is searched for an alias by the name _letter and if an alias  of
                 this  name  is defined, its value will be inserted on the input queue.  The letter must not
                 be one of the above meta-functions.
       M-[letter Soft-key - Your alias list is searched for an alias by the name __letter and if an alias of
                 this  name  is defined, its value will be inserted on the input queue.  This can be used to
                 program function keys on many terminals.
       M-.       The last word of the previous command is inserted on the line.  If preceded  by  a  numeric
                 parameter, the value of this parameter determines which word to insert rather than the last
                 word.
       M-_       Same as M-..
       M-*       Attempt file name generation on the current word.  An asterisk  is  appended  if  the  word
                 doesn't match any file or contain any special pattern characters.
       M-ESC     Command or file name completion as described above.
       ^I tab    Attempts  command  or  file  name  completion  as described above.  If a partial completion
                 occurs, repeating this will behave as if M-= were entered.  If no match is found or entered
                 after space, a tab is inserted.
       M-=       If  not preceded by a numeric parameter, it generates the list of matching commands or file
                 names as described above.  Otherwise, the word under the cursor is  replaced  by  the  item
                 corresponding  to  the value of the numeric parameter from the most recently generated com-mand command
                 mand or file list.  If the cursor is not on a word, it is inserted instead.
       ^U        Multiply parameter of next command by 4.
       \         Escape next character.  Editing characters, the user's erase, kill and interrupt  (normally
                 ^?)   characters may be entered in a command line or in a search string if preceded by a \.
                 The \ removes the next character's editing features (if any).
       M-^V      Display version of the shell.
       M-#       If the line does not begin with a #, a # is inserted at the beginning of the line and after
                 each  new-line,  and the line is entered.  This causes a comment to be inserted in the his-tory history
                 tory file.  If the line begins with a #, the # is deleted and one # after each new-line  is
                 also deleted.

   Vi Editing Mode.
       There are two typing modes.  Initially, when you enter a command you are in the input mode.  To edit,
       the user enters control mode by typing ESC (033) and moves the cursor to the point needing correction
       and  then inserts or deletes characters or words as needed.  Most control commands accept an optional
       repeat count prior to the command.

       When in vi mode on most systems, canonical processing is initially enabled and the  command  will  be
       echoed again if the speed is 1200 baud or greater and it contains any control characters or less than
       one second has elapsed since the prompt was printed.  The ESC character terminates canonical process-ing processing
       ing  for the remainder of the command and the user can then modify the command line.  This scheme has
       the advantages of canonical processing with the type-ahead echoing of raw mode.

       If the option viraw is also set, the terminal will always have canonical processing  disabled.   This
       mode  is  implicit  for  systems that do not support two alternate end of line delimiters, and may be
       helpful for certain terminals.

        Input Edit Commands
              By default the editor is in input mode.
              erase     (User defined erase character as defined by the stty  command,  usually  ^H  or  #.)
                        Delete previous character.
              ^W        Delete  the  previous blank separated word.  On some systems the viraw option may be
                        required for this to work.
              eof       As the first character of  the  line  causes  the  shell  to  terminate  unless  the
                        ignoreeof option is set.  Otherwise this character is ignored.
              lnext     (User  defined  literal  next  character  as  defined  by  the  stty(1) or ^V if not
                        defined.)  Removes the next character's editing features (if any).  On some  systems
                        the viraw option may be required for this to work.
              \         Escape the next erase or kill character.
              ^I tab    Attempts  command  or  file  name completion as described above and returns to input
                        mode.  If a partial completion occurs, repeating this  will  behave  as  if  =  were
                        entered  from  control  mode.  If no match is found or entered after space, a tab is
                        inserted.
        Motion Edit Commands
              These commands will move the cursor.
              [count]l  Cursor forward (right) one character.
              [count][C Cursor forward (right) one character.
              [count]w  Cursor forward one alpha-numeric word.
              [count]W  Cursor to the beginning of the next word that follows a blank.
              [count]e  Cursor to end of word.
              [count]E  Cursor to end of the current blank delimited word.
              [count]h  Cursor backward (left) one character.
              [count][D Cursor backward (left) one character.
              [count]b  Cursor backward one word.
              [count]B  Cursor to preceding blank separated word.
              [count]|  Cursor to column count.
              [count]fc Find the next character c in the current line.
              [count]Fc Find the previous character c in the current line.
              [count]tc Equivalent to f followed by h.
              [count]Tc Equivalent to F followed by l.
              [count];  Repeats count times, the last single character find command, f, F, t, or T.
              [count],  Reverses the last single character find command count times.
              0         Cursor to start of line.
              ^         Cursor to start of line.
              [H        Cursor to first non-blank character in line.
              $         Cursor to end of line.
              [Y        Cursor to end of line.
              %         Moves to balancing (, ), {, }, [, or ].  If cursor is not on one of the above  char-acters, characters,
                        acters, the remainder of the line is searched for the first occurrence of one of the
                        above characters first.
        Search Edit Commands
              These commands access your command history.
              [count]k  Fetch previous command.  Each time k is entered the previous command back in time is
                        accessed.
              [count]-  Equivalent to k.
              [count][A If  cursor  is  at  the end of the line it is equivalent to / with string^set to the
                        contents of the current line.  Otherwise, it is equivalent to k.
              [count]j  Fetch next command.  Each time j is entered the next  command  forward  in  time  is
                        accessed.
              [count]+  Equivalent to j.
              [count][B Equivalent to j.
              [count]G  The  command  number count is fetched.  The default is the least recent history com-mand. command.
                        mand.
              /string   Search backward through history for a previous command containing string.  String is
                        terminated  by  a `RETURN' or `NEW LINE'.  If string is preceded by a ^, the matched
                        line must begin with string.  If string is null, the previous string will be used.
              ?string   Same as / except that search will be in the forward direction.
              n         Search for next match of the last pattern to / or ?  commands.
              N         Search for next match of the last pattern to / or ?, but in reverse direction.
        Text Modification Edit Commands
              These commands will modify the line.
              a         Enter input mode and enter text after the current character.
              A         Append text to the end of the line.  Equivalent to $a.
              [count]cmotion
              c[count]motion
                        Delete current character through the character that motion would move the cursor  to
                        and  enter  input  mode.   If motion is c, the entire line will be deleted and input
                        mode entered.
              C         Delete the current character through the end of line and enter input mode.   Equiva-lent Equivalent
                        lent to c$.
              S         Equivalent to cc.
              [count]s  Replace characters under the cursor in input mode.
              D         Delete the current character through the end of line.  Equivalent to d$.
              [count]dmotion
              d[count]motion
                        Delete current character through the character that motion would move to.  If motion
                        is d , the entire line will be deleted.
              i         Enter input mode and insert text before the current character.
              I         Insert text before the beginning of the line.  Equivalent to 0i.
              [count]P  Place the previous text modification before the cursor.
              [count]p  Place the previous text modification after the cursor.
              R         Enter input mode and replace characters on the screen with characters you type over-lay overlay
                        lay fashion.
              [count]rc Replace  the  count character(s) starting at the current cursor position with c, and
                        advance the cursor.
              [count]x  Delete current character.
              [count]X  Delete preceding character.
              [count].  Repeat the previous text modification command.
              [count]~  Invert the case of the count character(s) starting at the  current  cursor  position
                        and advance the cursor.
              [count]_  Causes the count word of the previous command to be appended and input mode entered.
                        The last word is used if count is omitted.
              *         Causes an * to be appended to the current word and file name  generation  attempted.
                        If  no  match  is  found, it rings the bell.  Otherwise, the word is replaced by the
                        matching pattern and input mode is entered.
              \         Command or file name completion as described above.
        Other Edit Commands
              Miscellaneous commands.
              [count]ymotion
              y[count]motion
                        Yank current character through character that motion would move the  cursor  to  and
                        puts them into the delete buffer.  The text and cursor are unchanged.
              yy        Yanks the entire line.
              Y         Yanks from current position to end of line.  Equivalent to y$.
              u         Undo the last text modifying command.
              U         Undo all the text modifying commands performed on the line.
              [count]v  Returns  the command hist -e ${VISUAL:-${EDITOR:-vi}} count in the input buffer.  If
                        count is omitted, then the current line is used.
              ^L        Line feed and print current line.  Has effect only in control mode.
              ^J        (New line) Execute the current line, regardless of mode.
              ^M        (Return) Execute the current line, regardless of mode.
              #         If the first character of the command is a #, then this command deletes this  #  and
                        each  #  that  follows  a newline.  Otherwise, sends the line after inserting a # in
                        front of each line in the command.  Useful  for  causing  the  current  line  to  be
                        inserted  in the history as a comment and uncommenting previously commented commands
                        in the history file.
              [count]=  If count is not specified, it generates the list of matching commands or file  names
                        as  described  above.   Otherwise,  the word under the the cursor is replaced by the
                        count item from the most recently generated command or file list.  If the cursor  is
                        not on a word, it is inserted instead.
              @letter   Your alias list is searched for an alias by the name _letter and if an alias of this
                        name is defined, its value will be inserted on the input queue for processing.
              ^V        Display version of the shell.

   Built-in Commands.
       The following simple-commands are executed in the shell process.  Input/Output redirection is permit-ted. permitted.
       ted.   Unless  otherwise  indicated,  the output is written on file descriptor 1 and the exit status,
       when there is no syntax error, is zero.  Except for :, true, false,  echo,  newgrp,  and  login,  all
       built-in  commands  accept  -- to indicate end of options.  They also interpret the option --man as a
       request to display the man page onto standard error and -?  as a help request which  prints  a  usage
       message  on  standard error.  Commands that are preceded by one or two | symbols are special built-in
       commands and are treated specially in the following ways:
       1.     Variable assignment lists preceding the command remain in effect when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words following a command preceded by || that are in the format of a variable  assignment  are
              expanded  with the same rules as a variable assignment.  This means that tilde substitution is
              performed after the = sign and field splitting and file name  generation  are  not  performed.
              These are called declaration built-ins.

       | : [ arg ... ]
              The command only expands parameters.

       | . name [ arg ... ]
              If  name  is  a  function defined with the function name reserved word syntax, the function is
              executed in the current environment (as if it had been defined with the name() syntax.)   Oth-erwise Otherwise
              erwise  if  name  refers to a file, the file is read in its entirety and the commands are exe-cuted executed
              cuted in the current shell environment.  The search path specified by PATH is used to find the
              directory  containing  the  file.   If any arguments arg are given, they become the positional
              parameters while processing the .  command and the original positional parameters are restored
              upon  completion.   Otherwise the positional parameters are unchanged.  The exit status is the
              exit status of the last command executed.

       || alias [ -ptx ]  [ name[ =value  ] ] ...
              alias with no arguments prints the list of aliases in the form name=value on standard  output.
              The  -p  option  causes the word alias to be inserted before each one.  When one or more argu-ments arguments
              ments are given, an alias is defined for each name whose value is given.  A trailing space  in
              value  causes  the  next word to be checked for alias substitution.  The obsolete -t option is
              used to set and list tracked aliases.  The value of a tracked alias is the full pathname  cor-responding corresponding
              responding to the given name.  The value becomes undefined when the value of PATH is reset but
              the alias remains tracked.  Without the -t option, for each name  in  the  argument  list  for
              which  no  value is given, the name and value of the alias is printed.  The obsolete -x option
              has no effect.  The exit status is non-zero if a name is given, but no value, and no alias has
              been defined for the name.

       bg [ job... ]
              This  command  is  only on systems that support job control.  Puts each specified job into the
              background.  The current job is put in the background if job is not specified.  See Jobs for a
              description of the format of job.

       | break [ n ]
              Exit  from  the  enclosing for, while, until, or select loop, if any.  If n is specified, then
              break n levels.

       builtin [ -ds ] [ -f file ] [ name ... ]
              If name is not specified, and no -f option is specified, the built-ins are printed on standard
              output.  The -s option prints only the special built-ins.  Otherwise, each name represents the
              pathname whose basename is the name of the built-in.  The entry point function name is  deter-mined determined
              mined by prepending b_ to the built-in name.  The ISO C/C++ prototype is b_mycommand(int argc,
              char *argv[], void *context) for the builtin command mycommand where argv is array an of  argc
              elements  and  context  is  an  optional  pointer  to  a  Shell_t  structure  as  described in
              <ast/shell.h>.
              Special built-ins cannot be bound to a pathname or deleted.  The -d option deletes each of the
              given  built-ins.   On  systems  that  support  dynamic  loading, the -f option names a shared
              library containing the code for built-ins.  The shared library  prefix  and/or  suffix,  which
              depend  on the system, can be omitted.  Once a library is loaded, its symbols become available
              for subsequent invocations of builtin.  Multiple libraries  can  be  specified  with  separate
              invocations of the builtin command.  Libraries are searched in the reverse order in which they
              are specified.  When a library is loaded, it looks for a function in the library whose name is
              lib_init() and invokes this function with an argument of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
              This  command  can be in either of two forms.  In the first form it changes the current direc-tory directory
              tory to arg.  If arg is - the directory is changed to the previous directory.  The shell vari-able variable
              able  HOME  is  the default arg.  The variable PWD is set to the current directory.  The shell
              variable CDPATH defines the search path for the directory containing arg.  Alternative  direc-tory directory
              tory  names  are separated by a colon (:).  The default path is <null> (specifying the current
              directory).  Note that the current directory is specified by  a  null  path  name,  which  can
              appear  immediately  after the equal sign or between the colon delimiters anywhere else in the
              path list.  If arg begins with a / then the search path is not used.  Otherwise,  each  direc-tory directory
              tory in the path is searched for arg.
              The  second  form of cd substitutes the string new for the string old in the current directory
              name, PWD, and tries to change to this new directory.
              By default, symbolic link names are treated literally when finding the directory  name.   This
              is  equivalent  to  the  -L  option.   The -P option causes symbolic links to be resolved when
              determining the directory.  The last instance of -L or -P on the command line determines which
              method is used.
              The cd command may not be executed by rksh.  rksh93.

       command [ -pvxV ] name [ arg ... ]
              Without  the  -v or -V options, command executes name with the arguments given by arg.  The -p
              option causes a default path to be searched rather than the one defined by the value of  PATH.
              Functions  will  not be searched for when finding name.  In addition, if name refers to a spe-cial special
              cial built-in, none of the special properties associated with the leading daggers will be hon-ored. honored.
              ored.   (For example, the predefined alias redirect='command exec' prevents a script from ter-minating terminating
              minating when an invalid redirection is given.)  With the  -x  option,  if  command  execution
              would  result  in  a failure because there are too many arguments, errno E2BIG, the shell will
              invoke command name multiple times with a subset of the arguments on each  invocation.   Argu-ments Arguments
              ments that occur prior to the first word that expands to multiple arguments and after the last
              word that expands to multiple arguments will be passed on each invocation.   The  exit  status
              will  be the maximum invocation exit status.  With the -v option, command is equivalent to the
              built-in whence command described below.  The -V option causes command to act like whence  -v.

       | continue [ n ]
              Resume  the next iteration of the enclosing for, while, until, or select loop.  If n is speci-fied, specified,
              fied, then resume at the n-th enclosing loop.

       disown [ job... ]
              Causes the shell not to send a HUP signal to each given job, or all  active  jobs  if  job  is
              omitted, when a login shell terminates.

       echo [ arg ... ]
              When  the  first arg does not begin with a -, and none of the arguments contain a \, then echo
              prints each of its arguments separated by a space and terminated by  a  new-line.   Otherwise,
              the  behavior  of echo is system dependent and print or printf described below should be used.
              See echo(1) for usage and description.

       || enum [ -i  ] type[=(value ...) ]
              Creates a declaration command named type that is an integer type that allows one of the speci-fied specified
              fied  values  as  enumeration names.  If =(value ...) is omitted, then type must be an indexed
              array variable with at least two elements and the values are taken from this  array  variable.
              If -i is specified the values are case insensitive.

       | eval [ arg ... ]
              The arguments are read as input to the shell and the resulting command(s) executed.

       | exec [ -c ] [ -a name ] [ arg ... ]
              If  arg  is  given,  the command specified by the arguments is executed in place of this shell
              without creating a new process.  The -c option causes the environment  to  be  cleared  before
              applying  variable assignments associated with the exec invocation.  The -a option causes name
              rather than the first arg, to become argv[0] for the new process.  Input/output arguments  may
              appear  and affect the current process.  If arg is not given, the effect of this command is to
              modify file descriptors as prescribed by the input/output redirection list.  In this case, any
              file  descriptor  numbers  greater  than 2 that are opened with this mechanism are closed when
              invoking another program.

       | exit [ n ]
              Causes the shell to exit with the exit status specified by n.  The value  will  be  the  least
              significant  8 bits of the specified status.  If n is omitted, then the exit status is that of
              the last command executed.  An end-of-file will also cause the shell  to  exit  except  for  a
              shell which has the ignoreeof option (see set below) turned on.

       || export [ -p ] [ name[=value] ] ...
              If  name  is  not  given,  the names and values of each variable with the export attribute are
              printed with the values quoted in a manner that allows them to be re-input.  The  export  com-mand command
              mand is the same as typeset -x except that if you use export within a function, no local vari-able variable
              able is created.  The -p option causes the word export to be inserted before each one.  Other-wise, Otherwise,
              wise,  the given names are marked for automatic export to the environment of subsequently-exe-cuted subsequently-executed
              cuted commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
              This command is only on systems that support job control.  Each job specified  is  brought  to
              the  foreground  and waited for in the specified order.  Otherwise, the current job is brought
              into the foreground.  See Jobs for a description of the format of job.

       getconf [ name [ pathname ] ]
              Prints the current value of the configuration parameter  given  by  name.   The  configuration
              parameters  are  defined by the IEEE POSIX 1003.1 and IEEE POSIX 1003.2 standards.  (See path-conf(2) pathconf(2)
              conf(2) and sysconf(2).)  The pathname argument is required for parameters whose value depends
              on  the  location in the file system.  If no arguments are given, getconf prints the names and
              values of the current configuration parameters.  The pathname / is used for each of the param-eters parameters
              eters that requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
              Checks  arg  for  legal  options.   If arg is omitted, the positional parameters are used.  An
              option argument begins with a + or a -.  An option not beginning with + or - or  the  argument
              --  ends the options.  Options beginning with + are only recognized when optstring begins with
              a +.  optstring contains the letters that getopts recognizes.  If a letter is followed by a :,
              that  option  is expected to have an argument.  The options can be separated from the argument
              by blanks.  The option -?  causes getopts to generate a usage message on standard error.   The
              -a  argument  can  be used to specify the name to use for the usage message, which defaults to
              $0.
              getopts places the next option letter it finds inside variable vname each time it is  invoked.
              The  option letter will be prepended with a + when arg begins with a +.  The index of the next
              arg is stored in OPTIND.  The option argument, if any, gets stored in OPTARG.
              A leading : in optstring causes getopts to store the letter of an invalid  option  in  OPTARG,
              and to set vname to ?  for an unknown option and to : when a required option argument is miss-ing. missing.
              ing.  Otherwise, getopts prints an error message.  The exit status is non-zero when there  are
              no more options.
              There  is no way to specify any of the options :, +, -, ?, [, and ].  The option # can only be
              specified as the first option.

       hist [ -e ename  ] [ -nlr ] [ first [ last ] ]
       hist -s  [ old=new ] [ command ]
              In the first form, a range of commands from first to last is selected from the  last  HISTSIZE
              commands  that were typed at the terminal.  The arguments first and last may be specified as a
              number or as a string.  A string is used to locate the most recent command starting  with  the
              given  string.   A negative number is used as an offset to the current command number.  If the
              -l option is selected, the commands are listed on standard output.  Otherwise, the editor pro-gram program
              gram ename is invoked on a file containing these keyboard commands.  If ename is not supplied,
              then the value of the variable HISTEDIT is used.  If HISTEDIT is not set, then FCEDIT (default
              /bin/ed)  is  used as the editor.  When editing is complete, the edited command(s) is executed
              if the changes have been saved.  If last is not specified, then it will be set to  first.   If
              first  is  not specified, the default is the previous command for editing and -16 for listing.
              The option -r reverses the order of the commands and the option -n suppresses command  numbers
              when  listing.   In  the  second  form,  command  is  interpreted as first described above and
              defaults to the last command executed.  The resulting command is executed after  the  optional
              substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
              Lists  information  about each given job; or all active jobs if job is omitted.  The -l option
              lists process ids in addition to the normal information.  The -n  option  only  displays  jobs
              that  have stopped or exited since last notified.  The -p option causes only the process group
              to be listed.  See Jobs for a description of the format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -l [ sig ... ]
              Sends either the TERM (terminate) signal or the specified signal to the specified jobs or pro-cesses. processes.
              cesses.   Signals  are either given by number with the -n option or by name with the -s option
              (as given in <signal.h>, stripped of the prefix ``SIG'' with  the  exception  that  SIGCLD  is
              named  CHLD).   For  backward compatibility, the n and s can be omitted and the number or name
              placed immediately after the -.  If the signal being sent is TERM (terminate) or HUP (hangup),
              then  the job or process will be sent a CONT (continue) signal if it is stopped.  The argument
              job can be the process id of a process that is not a member of one of the  active  jobs.   See
              Jobs for a description of the format of job.  In the third form, kill -l, if sig is not speci-fied, specified,
              fied, the signal names are listed.  Otherwise, for each sig that is a name, the  corresponding
              signal  number is listed.  For each sig that is a number, the signal name corresponding to the
              least significant 8 bits of sig is listed.

       let arg ...
              Each arg is a separate arithmetic expression  to  be  evaluated.   See  Arithmetic  Evaluation
              above, for a description of arithmetic expression evaluation.
              The exit status is 0 if the value of the last expression is non-zero, and 1 otherwise.

       | newgrp [ arg ... ]
              Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
              With no options or with option - or --, each arg is printed on standard output.  The -f option
              causes the arguments to be printed as described by printf.  In this  case,  any  e,  n,  r,  R
              options  are  ignored.   Otherwise,  unless the -C, -R, -r, or -v are specified, the following
              escape conventions will be applied:
              \a     The alert character (ascii 07).
              \b     The backspace character (ascii 010).
              \c     Causes print to end without processing more arguments and not adding a new-line.
              \f     The formfeed character (ascii 014).
              \n     The new-line character (ascii 012).
              \r     The carriage return character (ascii 015).
              \t     The tab character (ascii 011).
              \v     The vertical tab character (ascii 013).
              \E     The escape character (ascii 033).
              \\     The backslash character \.
              \0x    The character defined by the 1, 2, or 3-digit octal string given by x.

              The -R option will print all subsequent arguments and options other than -n.   The  -e  causes
              the  above  escape  conventions to be applied.  This is the default behavior.  It reverses the
              effect of an earlier -r.  The -p option causes the arguments to be written onto  the  pipe  of
              the  process  spawned  with |& instead of standard output.  The -v option treats each arg as a
              variable name and writes the value in the printf %B format.  The -C option treats each arg  as
              a variable name and writes the value in the printf %#B format.  The -s option causes the argu-ments arguments
              ments to be written onto the history file instead of standard output.  The -u  option  can  be
              used  to  specify  a  one  digit  file descriptor unit number unit on which the output will be
              placed.  The default is 1.  If the option -n is used, no new-line is added to the output.

       printf format [ arg ... ]
              The arguments arg are printed on standard output in  accordance  with  the  ANSI-C  formatting
              rules associated with the format string format.  If the number of arguments exceeds the number
              of format specifications, the format string is reused to format remaining arguments.  The fol-lowing following
              lowing extensions can also be used:
              %b     A  %b  format  can be used instead of %s to cause escape sequences in the corresponding
                     arg to be expanded as described in print.
              %B     A %B option causes each of the arguments to be treated as variable names and the binary
                     value  of variable will be printed.  The alternate flag # causes a compound variable to
                     be output on a single line.  This is most useful for compound variables  and  variables
                     whose attribute is -b.
              %H     A  %H  format  can be used instead of %s to cause characters in arg that are special in
                     HTML and XML to be output as their entity name.
              %P     A %P format can be used instead of %s to cause arg to be  interpreted  as  an  extended
                     regular expression and be printed as a shell pattern.
              The format modifier
                     L  can be used with the %c and %s formats to treat precision as character width instead
                     of byte count.
              The format modifier
                     , can be used with the %d and %f formats to treat separate groups of  digits  with  the
                     grouping delimiter which is %d in the C locale.
              %R     A %R format can be used instead of %s to cause arg to be interpreted as a shell pattern
                     and to be printed as an extended regular expression.
              %q     A %q format can be used instead of %s to cause the resulting string to be quoted  in  a
                     manner than can be reinput to the shell.
              %(date-format)T
                     A  %(date-format)T  format can be use to treat an argument as a date/time string and to
                     format the date/time according to the date-format as defined for the date(1) command.
              %Z     A %Z format will output a byte whose value is 0.
              %d     The precision field of the %d format can be followed by a .  and the output  base.   In
                     this case, the # flag character causes base# to be prepended.
              #      The  # flag when used with the d specifier without an output base, causes the output to
                     be displayed in thousands units with one of the suffixes k M G T P E  to  indicate  the
                     unit.   The  # flag when used with the i specifier causes the output to be displayed in
                     1024 with one of the suffixes Ki Mi Gi Ti Pi Ei to indicate the unit.
              =      The = flag has been added to center the output within the specified field width.


       pwd [ -LP ]
              Outputs the value of the current working directory.  The -L option is the default;  it  prints
              the  logical name of the current directory.  If the -P option is given, all symbolic links are
              resolved from the name.  The last instance of -L or -P on the command  line  determines  which
              method is used.

       read  [  -ACprsv  ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u unit] [ vname?prompt ] [ vname
       ... ]
              The shell input mechanism.  One line is read and is broken up into fields using the characters
              in IFS as separators.  The escape character, \, is used to remove any special meaning for  the
              next  character  and  for line continuation.  The -d option causes the read to continue to the
              first character of delim rather than new-line.  The -n option causes at most n bytes  to  read
              rather  a  full line but will return when reading from a slow device as soon as any characters
              have been read.  The -N option causes exactly n to be read  unless  an  end-of-file  has  been
              encountered  or the read times out because of the -t option.  In raw mode, -r, the \ character
              is not treated specially.  The first field is assigned to the first vname, the second field to
              the  second  vname, etc., with leftover fields assigned to the last vname.  When vname has the
              binary attribute and -n or -N is specified, the bytes that are read are stored  directly  into
              the  variable.   If  the  -v is specified, then the value of the first vname will be used as a
              default value when reading from a terminal device.  The -A option causes the variable vname to
              be  unset and each field that is read to be stored in successive elements of the indexed array
              vname.  The -C option causes the variable vname to be read as  a  compound  variable.   Blanks
              will  be  ignored when finding the beginning open parenthesis.  The -p option causes the input
              line to be taken from the input pipe of a process spawned by the shell using |&.   If  the  -s
              option  is  present,  the input will be saved as a command in the history file.  The option -u
              can be used to specify a one digit file descriptor unit unit to read from.  The file  descrip-tor descriptor
              tor  can  be opened with the exec special built-in command.  The default value of unit n is 0.
              The option -t is used to specify a timeout in seconds when reading from a  terminal  or  pipe.
              If  vname  is  omitted,  then  REPLY is used as the default vname.  An end-of-file with the -p
              option causes cleanup for this process so that another can be spawned.  If the first  argument
              contains  a ?, the remainder of this word is used as a prompt on standard error when the shell
              is interactive.  The exit status is 0 unless an end-of-file is encountered or read  has  timed
              out.

       || readonly [ -p ] [ vname[=value] ] ...
              If  vname  is  not given, the names and values of each variable with the readonly attribute is
              printed with the values quoted in a manner that allows them to be re-inputted.  The -p  option
              causes  the  word  readonly  to  be inserted before each one.  Otherwise, the given vnames are
              marked readonly and these names cannot be changed by subsequent assignment.  When  defining  a
              type, if the value of a readonly sub-variable is not defined the value is required when creat-ing creating
              ing each instance.

       | return [ n ]
              Causes a shell function or .  script to return to the invoking script  with  the  exit  status
              specified by n.  The value will be the least significant 8 bits of the specified status.  If n
              is omitted, then the return status is that of the last command executed.  If return is invoked
              while not in a function or a .  script, then it behaves the same as exit.

       | set [ +-BCGabefhkmnoprstuvx ] [ +-o [ option ] ] ... [ +-A vname ]  [ arg ... ]
              The options for this command have meaning as follows:
              -A      Array  assignment.   Unset  the variable vname and assign values sequentially from the
                      arg list.  If +A is used, the variable vname is not unset first.
              -B      Enable brace pattern field generation.  This is the default behavior.
              -B      Enable brace group expansion.  On by default.
              -C      Prevents redirection > from truncating existing files.  Files  that  are  created  are
                      opened with the O_EXCL mode.  Requires >| to truncate a file when turned on.
              -G      Causes  the  pattern ** by itself to match files and zero or more directories and sub-directories subdirectories
                      directories when used for file name generation.  If followed by a /  only  directories
                      and sub-directories are matched.
              -a      All subsequent variables that are defined are automatically exported.
              -b      Prints  job  completion messages as soon as a background job changes state rather than
                      waiting for the next prompt.
              -e      Unless contained in a || or && command, or the command following an if while or  until
                      command  or in the pipeline following !, if a command has a non-zero exit status, exe-cute execute
                      cute the ERR trap, if set, and exit.  This mode is disabled while reading profiles.
              -f      Disables file name generation.
              -h      Each command becomes a tracked alias when first encountered.
              -k      (Obsolete). All variable assignment arguments are placed in the environment for a com-mand, command,
                      mand, not just those that precede the command name.
              -m      Background  jobs  will run in a separate process group and a line will print upon com-pletion. completion.
                      pletion.  The exit status of background jobs is reported in a completion message.   On
                      systems  with  job  control,  this  option  is turned on automatically for interactive
                      shells.
              -n      Read commands and check them for syntax errors, but do not execute them.  Ignored  for
                      interactive shells.
              -o      The following argument can be one of the following option names:
                      allexport
                              Same as -a.
                      errexit Same as -e.
                      bgnice  All background jobs are run at a lower priority.  This is the default mode.
                      braceexpand
                              Same as -B.
                      emacs   Puts you in an emacs style in-line editor for command entry.
                      globstar
                              Same as -G.
                      gmacs   Puts you in a gmacs style in-line editor for command entry.
                      ignoreeof
                              The shell will not exit on end-of-file.  The command exit must be used.
                      keyword Same as -k.
                      markdirs
                              All  directory  names  resulting  from  file name generation have a trailing /
                              appended.
                      monitor Same as -m.
                      multiline
                              The built-in editors will use multiple lines on the screen for lines that  are
                              longer than the width of the screen.  This may not work for all terminals.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Do not save function definitions in the history file.
                      notify  Same as -b.
                      nounset Same as -u.
                      pipefail
                              A  pipeline  will  not complete until all components of the pipeline have com-pleted, completed,
                              pleted, and the return value will be the value of the last non-zero command to
                              fail or zero if no command has failed.
                      showme  When enabled, simple commands or pipelines preceded by a semicolon (;) will be
                              displayed as if the xtrace option were enabled but will not be executed.  Oth-erwise, Otherwise,
                              erwise, the leading ; will be ignored.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      trackall
                              Same as -h.
                      vi      Puts  you in insert mode of a vi style in-line editor until you hit the escape
                              character 033.  This puts you in control mode.  A return sends the line.
                      viraw   Each character is processed as it is typed in vi mode.
                      xtrace  Same as -x.
                      If no option name is supplied, then the current option settings are printed.
              -p      Disables processing of the $HOME/.profile file and  uses  the  file  /etc/suid_profile
                      instead  of  the  ENV  file.   This mode is on whenever the effective uid (gid) is not
                      equal to the real uid (gid).  Turning this off causes the effective uid and gid to  be
                      set to the real uid and gid.
              -r      Enables the restricted shell.  This option cannot be unset once set.
              -s      Sort the positional parameters lexicographically.
              -t      (Obsolete).  Exit after reading and executing one command.
              -u      Treat unset parameters as an error when substituting.
              -v      Print shell input lines as they are read.
              -x      Print commands and their arguments as they are executed.
              --      Do  not  change  any of the options; useful in setting $1 to a value beginning with -.
                      If no arguments follow this option then the positional parameters are unset.

              As an obsolete feature, if the first arg is - then the -x and -v options are  turned  off  and
              the  next arg is treated as the first argument.  Using + rather than - causes these options to
              be turned off.  These options can also be used upon invocation of the shell.  The current  set
              of options may be found in $-.  Unless -A is specified, the remaining arguments are positional
              parameters and are assigned, in order, to $1 $2 ....  If no  arguments  are  given,  then  the
              names and values of all variables are printed on the standard output.

       | shift [ n ]
              The positional parameters from $n+1 ...  are renamed $1 ... , default n is 1.  The parameter n
              can be any arithmetic expression that evaluates to a non-negative number less than or equal to
              $#.

       sleep seconds
              Suspends  execution  for  the number of decimal seconds or fractions of a second given by sec-onds. seconds.
              onds.

       | trap [ -p ] [ action ] [ sig ] ...
              The -p option causes the trap action associated with each trap as specified by  the  arguments
              to  be printed with appropriate quoting.  Otherwise, action will be processed as if it were an
              argument to eval when the shell receives signal(s) sig.  Each sig can be given as a number  or
              as the name of the signal.  Trap commands are executed in order of signal number.  Any attempt
              to set a trap on a signal that was ignored on entry to the current shell is  ineffective.   If
              action  is omitted and the first sig is a number, or if action is -, then the trap(s) for each
              sig are reset to their original values.  If action is the null  string  then  this  signal  is
              ignored  by  the shell and by the commands it invokes.  If sig is ERR then action will be exe-cuted executed
              cuted whenever a command has a non-zero exit status.  If sig is DEBUG then action will be exe-cuted executed
              cuted  before each command.  The variable .sh.command will contain the contents of the current
              command line when action is running.  If the exit status of the trap is 2 the command will not
              be executed.  If the exit status of the trap is 255 and inside a function or a dot script, the
              function or dot script will return.  If sig is 0 or EXIT and the trap  statement  is  executed
              inside  the  body of a function defined with the function name syntax, then the command action
              is executed after the function completes.  If sig is 0 or EXIT for  a  trap  set  outside  any
              function  then  the  command action is executed on exit from the shell.  If sig is KEYBD, then
              action will be executed whenever a key is read while in emacs, gmacs, or vi  mode.   The  trap
              command with no arguments prints a list of commands associated with each signal number.

       An  exit  or return without an argument in a trap action will preserve the exit status of the command
       that invoked the trap.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       || typeset [ +-ACHSflbnprtux ] [ +-EFLRXZi[n] ]   [ +-M  [ mapname ] ] [ -T  [ tname=(assign_list)  ]
       ] [ -h str ] [ -a [type] ] [ vname[=value ]  ] ...
              Sets attributes and values for shell variables and functions.  When invoked inside a  function
              defined  with  the  function name syntax, a new instance of the variable vname is created, and
              the variable's value and type are restored when the function completes.  The following list of
              attributes may be specified:
              -A     Declares  vname  to be an associative array.  Subscripts are strings rather than arith-metic arithmetic
                     metic expressions.
              -C     causes each vname to be a compound variable.  value names a  compound  variable  it  is
                     copied into vname.  Otherwise, it unsets each vname.
              -a     Declares vname to be an indexed array.  If type is specified, it must be the name of an
                     enumeration type created with the enum command and it allows enumeration  constants  to
                     be used as subscripts.
              -E     Declares  vname  to  be a double precision floating point number.  If n is non-zero, it
                     defines the number of significant figures that are used when expanding  vname.   Other-wise, Otherwise,
                     wise, ten significant figures will be used.
              -F     Declares  vname  to  be a double precision floating point number.  If n is non-zero, it
                     defines the number of places after the decimal  point  that  are  used  when  expanding
                     vname.  Otherwise ten places after the decimal point will be used.
              -H     This option provides UNIX to host-name file mapping on non-UNIX machines.
              -L     Left  justify  and  remove leading blanks from value.  If n is non-zero, it defines the
                     width of the field, otherwise it is determined by the  width  of  the  value  of  first
                     assignment.  When the variable is assigned to, it is filled on the right with blanks or
                     truncated, if necessary, to fit into the field.  The -R option is turned off.
              -M     Use the character mapping mapping defined by wctrans(3).  such as tolower  and  toupper
                     when  assigning  a  value to each of the specified operands.  When mapping is specified
                     and there are not operands, all variables that use this mapping are written to standard
                     output.   When  mapping  is omitted and there are no operands, all mapped variables are
                     written to standard output.
              -R     Right justify and fill with leading blanks.  If n is non-zero, it defines the width  of
                     the  field,  otherwise  it is determined by the width of the value of first assignment.
                     The field is left filled with blanks or truncated from the end if the variable is reas-signed. reassigned.
                     signed.  The -L option is turned off.
              -S     When  used  within  the  assign_list of a type definition, it causes the specified sub-variable subvariable
                     variable to be shared by all instances of  the  type.   When  used  inside  a  function
                     defined  with  the  function  reserved word, the specified variables will have function
                     static scope.  Otherwise, the variable is unset  prior  to  processing  the  assignment
                     list.
              -T     If  followed  by  tname, it creates a type named by tname using the compound assignment
                     assign_list to tname.  Otherwise, it writes all the type definitions to  standard  out-put. output.
                     put.
              -X     Declares  vname to be a double precision floating point number and expands using the %a
                     format of ISO-C99.  If n is non-zero, it defines the number of  hex  digits  after  the
                     radix point that is used when expanding vname.  The default is 10.
              -Z     Right  justify  and fill with leading zeros if the first non-blank character is a digit
                     and the -L option has not been set.  Remove leading zeros if the -L option is also set.
                     If  n is non-zero, it defines the width of the field, otherwise it is determined by the
                     width of the value of first assignment.
              -f     The names refer to function names rather than variable names.  No  assignments  can  be
                     made  and  the only other valid options are -S, -t, -u and -x.  The -S can be used with
                     discipline functions defined in a type to indicate that the function is static.  For  a
                     static  function,  the same method will be used by all instances of that type no matter
                     which instance references it.  In additon, it can only use value of variables from  the
                     original  type  definition.  These discipline functions cannot be redefined in any type
                     instance.  The -t option turns on execution tracing for this function.  The  -u  option
                     causes  this  function  to be marked undefined.  The FPATH variable will be searched to
                     find the function definition when the function is referenced.  If no options other than
                     -f is specified, then the function definition will be displayed on standard output.  If
                     +f is specified, then a line containing the function name followed by a  shell  comment
                     containing  the  line number and path name of the file where this function was defined,
                     if any, is displayed.
              -b     The variable can hold any number of bytes of data.  The data can  be  text  or  binary.
                     The  value is represented by the base64 encoding of the data.  If -Z is also specified,
                     the size in bytes of the data in the buffer will be determined by the  size  associated
                     with the -Z.  If the base64 string assigned results in more data, it will be truncated.
                     Otherwise, it will be filled with bytes whose value is zero.  The printf format %B  can
                     be  used to output the actual data in this buffer instead of the base64 encoding of the
                     data.
              -h     Used within type definitions to add information when generating information  about  the
                     sub-variable  on  the  man page.  It is ignored when used outside of a type definition.
                     When used with -f the information is associated with the corresponding discipline func-tion. function.
                     tion.
              -i     Declares  vname  to  be  represented  internally as integer.  The right hand side of an
                     assignment is evaluated as an arithmetic expression when assigning to an integer.  If n
                     is  non-zero,  it defines the output arithmetic base, otherwise the output base will be
                     ten.
              -l     Used with -i, -E or -F, to indicate long integer, or long float.  Otherwise, all upper-case uppercase
                     case characters are converted to lower-case.  The upper-case option, -u, is turned off.
                     Equivalent to -M tolower .
              -n     Declares vname to be a reference to the variable whose name is defined by the value  of
                     variable  vname.   This is usually used to reference a variable inside a function whose
                     name has been passed as an argument.
              -p     The name, attributes and values for the given vnames are written on standard output  in
                     a  form  that  can be used as shell input.  If +p is specified, then the values are not
                     displayed.
              -r     The given vnames are marked readonly and these names cannot be  changed  by  subsequent
                     assignment.
              -t     Tags  the variables.  Tags are user definable and have no special meaning to the shell.
              -u     When given along with -i, specifies unsigned integer.  Otherwise, all lower-case  char-acters characters
                     acters are converted to upper-case.  The lower-case option, -l, is turned off.  Equiva-lent Equivalent
                     lent to -M toupper .
              -x     The given vnames are marked for automatic export to the  environment  of  subsequently-executed subsequentlyexecuted
                     executed commands.  Variables whose names contain a .  cannot be exported.

              The -i attribute cannot be specified along with -R, -L, -Z, or -f.

              Using + rather than - causes these options to be turned off.  If no vname arguments are given,
              a list of vnames (and optionally the values) of the variables is  printed.   (Using  +  rather
              than  -  keeps  the  values from being printed.)  The -p option causes typeset followed by the
              option letters to be printed before each name rather than the names of the  options.   If  any
              option  other  than  -p is given, only those variables which have all of the given options are
              printed.  Otherwise, the vnames and attributes of  all  variables  that  have  attributes  are
              printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
              Set  or  display a resource limit.  The available resource limits are listed below.  Many sys-tems systems
              tems do not support one or more of these limits.  The limit for a specified  resource  is  set
              when  limit is specified.  The value of limit can be a number in the unit specified below with
              each resource, or the value unlimited.  The -H and -S options specify whether the  hard  limit
              or  the soft limit for the given resource is set.  A hard limit cannot be increased once it is
              set.  A soft limit can be increased up to the value of the hard limit.  If neither the H nor S
              option  is  specified,  the limit applies to both.  The current resource limit is printed when
              limit is omitted.  In this case, the soft limit is printed unless H is specified.   When  more
              than one resource is specified, then the limit name and unit is printed before the value.
              -a     Lists all of the current resource limits.
              -c     The number of 512-byte blocks on the size of core dumps.
              -d     The number of K-bytes on the size of the data area.
              -f     The number of 512-byte blocks on files that can be written by the current process or by
                     child processes (files of any size may be read).
              -m     The number of K-bytes on the size of physical memory.
              -n     The number of file descriptors plus 1.
              -p     The number of 512-byte blocks for pipe buffering.
              -s     The number of K-bytes on the size of the stack area.
              -t     The number of CPU seconds to be used by each process.
              -v     The number of K-bytes for virtual memory.

              If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
              The user file-creation mask is set to mask (see umask(2)).  mask can either be an octal number
              or  a  symbolic  value  as described in chmod(1).  If a symbolic value is given, the new umask
              value is the complement of the result of applying mask to the complement of the previous umask
              value.   If  mask  is omitted, the current value of the mask is printed.  The -S option causes
              the mode to be printed as a symbolic value.  Otherwise, the mask is printed in octal.

       | unalias [ -a ] name ...
              The aliases given by the list of names are removed from the alias list.  The -a option  causes
              all the aliases to be unset.

       |unset [ -fnv ] vname ...
              The  variables  given  by  the  list  of vnames are unassigned, i.e., except for sub-variables
              within a type, their values and attributes are erased.  For sub-variables of a type, the  val-ues values
              ues  are  reset  to  the default value from the type definition.  Readonly variables cannot be
              unset.  If the -f option is set, then the names refer to function names.  If the -v option  is
              set,  then  the  names refer to variable names.  The -f option overrides -v.  If -n is set and
              name is a name reference, then name will be unset rather than the variable that it references.
              The  default  is  equivalent to -v.  Unsetting LINENO, MAILCHECK, OPTARG, OPTIND, RANDOM, SEC-ONDS, SECONDS,
              ONDS, TMOUT, and _ removes their special meaning even if they are subsequently assigned to.

       wait [ job ... ]
              Wait for the specified job and report its termination status.  If job is not given,  then  all
              currently active child processes are waited for.  The exit status from this command is that of
              the last process waited for if job is specified;  otherwise  it  is  zero.   See  Jobs  for  a
              description of the format of job.

       whence [ -afpv ] name ...
              For each name, indicate how it would be interpreted if used as a command name.
              The  -v  option produces a more verbose report.  The -f option skips the search for functions.
              The -p option does a path search for name even if name is an alias, a function, or a  reserved
              word.   The  -p option turns off the -v option.  The -a option is similar to the -v option but
              causes all interpretations of the given name to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument zero  ($0)  is  -,  then  the
       shell  is  assumed  to  be a login shell and commands are read from /etc/profile and then from either
       .profile in the current directory or $HOME/.profile, if either file exists.   Next,  for  interactive
       shells,  commands  are  read from the file named by performing parameter expansion, command substitu-tion, substitution,
       tion, and arithmetic substitution on the value of the environment variable ENV if  the  file  exists.
       If  the -s option is not present and arg and a file by the name of arg exists, then it reads and exe-cutes executes
       cutes this script.  Otherwise, if the first arg does not contain a /, a path search is  performed  on
       the  first arg to determine the name of the script to execute.  The script arg must have execute per-mission permission
       mission and any setuid and setgid settings will be ignored.  If the script is not found on the  path,
       arg  is processed as if it named a built-in command or function.  Commands are then read as described
       below; the following options are interpreted by the shell when it is invoked:

       -D      Do not execute the script, but output the set of double  quoted  strings  preceded  by  a  $.
               These strings are needed for localization of the script to different locales.
       -E      Reads  the  file  named  by the ENV variable or by $HOME/.kshrc if not defined after the pro-files. profiles.
               files.
       -c        If the -c option is present, then commands are read from  the  first  arg.   Any  remaining
                 arguments become positional parameters starting at 0.
       -s        If  the  -s  option  is  present or if no arguments remain, then commands are read from the
                 standard input.  Shell output, except for the output of the Special Commands listed  above,
                 is written to file descriptor 2.
       -i        If the -i option is present or if the shell input and output are attached to a terminal (as
                 told by tcgetattr(2)), then this shell is interactive.  In this case TERM  is  ignored  (so
                 that  kill  0  does  not kill an interactive shell) and INTR is caught and ignored (so that
                 wait is interruptible).  In all cases, QUIT is ignored by the shell.
       -r        If the -r option is present, the shell is a restricted shell.
       -D        A list of all double quoted strings that are preceded by a $ will be  printed  on  standard
                 output  and  the shell will exit.  This set of strings will be subject to language transla-tion translation
                 tion when the locale is not C or POSIX.  No commands will be executed.

       -P        If -P or -o profile is present, the shell is a profile shell (see pfexec(1)).

       -R filename
                 The -R filename option is used to generate a cross reference database that can be used by a
                 separate utility to find definitions and references for variables and commands.

       The  remaining options and arguments are described under the set command above.  An optional - as the
       first argument is ignored.

   Rksh Only.
       Rksh is used to set up login names and execution environments whose capabilities are more  controlled
       than those of the standard shell.  The actions of rksh are identical to those of ksh, except that the
       following are disallowed:
              Unsetting the restricted option.
              changing directory (see cd(1)),
              setting or unsetting the value or attributes of SHELL, ENV, FPATH, or PATH,
              specifying path or command names containing /,
              redirecting output (>, >|, <>, and >>).
              adding or deleting built-in commands.
              using command -p to invoke a command.

       The restrictions above are enforced after .profile and the ENV files are interpreted.

       When a command to be executed is found to be a shell procedure,  rksh  invokes  ksh  to  execute  it.
       Thus,  it  is possible to provide to the end-user shell procedures that have access to the full power
       of the standard shell, while imposing a limited menu of commands; this scheme assumes that  the  end-user enduser
       user does not have write and execute permissions in the same directory.

       The  net  effect  of  these  rules  is that the writer of the .profile has complete control over user
       actions, by performing guaranteed setup actions and leaving the  user  in  an  appropriate  directory
       (probably not the login directory).

       The  system  administrator often sets up a directory of commands (e.g., /usr/rbin) that can be safely
       invoked by rksh.

EXIT STATUS
       Errors detected by the shell, such as syntax errors, cause the shell to return a non-zero  exit  sta-tus. status.
       tus.   If  the  shell  is being used non-interactively, then execution of the shell file is abandoned
       unless the error occurs inside a subshell in which case the subshell is  abandoned.   Otherwise,  the
       shell  returns  the  exit status of the last command executed (see also the exit command above).  Run
       time errors detected by the shell are reported by printing the command or function name and the error
       condition.   If  the line number that the error occurred on is greater than one, then the line number
       is also printed in square brackets ([]) after the command or function name.

FILES
       /etc/profile
              The system wide initialization file, executed for login shells.

       $HOME/.profile
              The personal initialization file, executed for login shells after /etc/profile.

       $HOME/..kshrc
              Default personal initialization file, executed for interactive shells when ENV is not set.

       /etc/suid_profile
              Alternative initialization file, executed instead of the personal initialization file when the
              real and effective user or group id do not match.

       /dev/null
              NULL device

SEE ALSO
       cat(1),  cd(1),  chmod(1),  cut(1), egrep(1), echo(1), emacs(1), env(1), fgrep(1), gmacs(1), grep(1),
       newgrp(1), pfexec(1), stty(1), test(1),  umask(1),  vi(1),  dup(2),  exec(2),  fork(2),  getpwnam(3),
       ioctl(2),  lseek(2),  paste(1),  pathconf(2),  pipe(2),  sysconf(2),  umask(2),  ulimit(2),  wait(2),
       wctrans(3), rand(3), a.out(5), profile(5), environ(7).

       Morris I. Bolsky and David G. Korn, The New KornShell  Command  and  Programming  Language,  Prentice
       Hall, 1995.

       POSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE, 1993.

CAVEATS
       If  a  command  is executed, and then a command with the same name is installed in a directory in the
       search path before the directory where the original command was found, the  shell  will  continue  to
       exec the original command.  Use the -t option of the alias command to correct this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe character |.

       Using  the  hist built-in command within a compound command will cause the whole command to disappear
       from the history file.

       The built-in command . file reads the whole file before any commands are executed.  Therefore,  alias
       and unalias commands in the file will not apply to any commands defined in the file.

       Traps  are not processed while a job is waiting for a foreground process.  Thus, a trap on CHLD won't
       be executed until the foreground job terminates.

       It is a good idea to leave a space after the comma operator in arithmetic expressions to prevent  the
       comma from being interpreted as the decimal point character in certain locales.



                                                                                                      KSH(1)

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