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GETCAP(3)                BSD Library Functions Manual                GETCAP(3)

NAME
     cgetent, cgetset, cgetmatch, cgetcap, cgetnum, cgetstr, cgetustr, cgetfirst, cgetnext, cgetclose --capability -capability
     capability database access routines

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdlib.h>

     int
     cgetent(char **buf, char **db_array, const char *name);

     int
     cgetset(const char *ent);

     int
     cgetmatch(const char *buf, const char *name);

     char *
     cgetcap(char *buf, const char *cap, int type);

     int
     cgetnum(char *buf, const char *cap, long *num);

     int
     cgetstr(char *buf, const char *cap, char **str);

     int
     cgetustr(char *buf, const char *cap, char **str);

     int
     cgetfirst(char **buf, char **db_array);

     int
     cgetnext(char **buf, char **db_array);

     int
     cgetclose(void);

DESCRIPTION
     The cgetent() function extracts the capability name from the database specified by the NULL terminated
     file array db_array and returns a pointer to a malloc(3)'d copy of it in buf.  The cgetent() function
     will first look for files ending in .db (see cap_mkdb(1)) before accessing the ASCII file.  The buf
     argument must be retained through all subsequent calls to cgetmatch(), cgetcap(), cgetnum(), cgetstr(),
     and cgetustr(), but may then be free(3)'d.  On success 0 is returned, 1 if the returned record contains
     an unresolved tc expansion, -1 if the requested record could not be found, -2 if a system error was
     encountered (could not open/read a file, etc.) also setting errno, and -3 if a potential reference loop
     is detected (see tc= comments below).

     The cgetset() function enables the addition of a character buffer containing a single capability record
     entry to the capability database.  Conceptually, the entry is added as the first ``file'' in the data-base, database,
     base, and is therefore searched first on the call to cgetent().  The entry is passed in ent.  If ent is
     NULL, the current entry is removed from the database.  A call to cgetset() must precede the database
     traversal.  It must be called before the cgetent() call.  If a sequential access is being performed
     (see below), it must be called before the first sequential access call (cgetfirst() or cgetnext()), or
     be directly preceded by a cgetclose() call.  On success 0 is returned and -1 on failure.

     The cgetmatch() function will return 0 if name is one of the names of the capability record buf, -1 if
     not.

     The cgetcap() function searches the capability record buf for the capability cap with type type.  A
     type is specified using any single character.  If a colon (`:') is used, an untyped capability will be
     searched for (see below for explanation of types).  A pointer to the value of cap in buf is returned on
     success, NULL if the requested capability could not be found.  The end of the capability value is sig-naled signaled
     naled by a `:' or ASCII NUL (see below for capability database syntax).

     The cgetnum() function retrieves the value of the numeric capability cap from the capability record
     pointed to by buf.  The numeric value is returned in the long pointed to by num.  0 is returned on suc-cess, success,
     cess, -1 if the requested numeric capability could not be found.

     The cgetstr() function retrieves the value of the string capability cap from the capability record
     pointed to by buf.  A pointer to a decoded, NUL terminated, malloc(3)'d copy of the string is returned
     in the char * pointed to by str.  The number of characters in the decoded string not including the
     trailing NUL is returned on success, -1 if the requested string capability could not be found, -2 if a
     system error was encountered (storage allocation failure).

     The cgetustr() function is identical to cgetstr() except that it does not expand special characters,
     but rather returns each character of the capability string literally.

     The cgetfirst() and cgetnext() functions comprise a function group that provides for sequential access
     of the NULL pointer terminated array of file names, db_array.  The cgetfirst() function returns the
     first record in the database and resets the access to the first record.  The cgetnext() function
     returns the next record in the database with respect to the record returned by the previous cgetfirst()
     or cgetnext() call.  If there is no such previous call, the first record in the database is returned.
     Each record is returned in a malloc(3)'d copy pointed to by buf.  Tc expansion is done (see tc= com-ments comments
     ments below).  Upon completion of the database 0 is returned, 1 is returned upon successful return of
     record with possibly more remaining (we have not reached the end of the database yet), 2 is returned if
     the record contains an unresolved tc expansion, -1 is returned if a system error occurred, and -2 is
     returned if a potential reference loop is detected (see tc= comments below).  Upon completion of data-base database
     base (0 return) the database is closed.

     The cgetclose() function closes the sequential access and frees any memory and file descriptors being
     used.  Note that it does not erase the buffer pushed by a call to cgetset().

CAPABILITY DATABASE SYNTAX
     Capability databases are normally ASCII and may be edited with standard text editors.  Blank lines and
     lines beginning with a `#' are comments and are ignored.  Lines ending with a `\' indicate that the
     next line is a continuation of the current line; the `\' and following newline are ignored.  Long lines
     are usually continued onto several physical lines by ending each line except the last with a `\'.

     Capability databases consist of a series of records, one per logical line.  Each record contains a
     variable number of `:'-separated fields (capabilities).  Empty fields consisting entirely of white
     space characters (spaces and tabs) are ignored.

     The first capability of each record specifies its names, separated by `|' characters.  These names are
     used to reference records in the database.  By convention, the last name is usually a comment and is
     not intended as a lookup tag.  For example, the vt1__ record from the termcap(5) database begins:

           d0|vt100|vt100-am|vt100am|dec vt100:

     giving four names that can be used to access the record.

     The remaining non-empty capabilities describe a set of (name, value) bindings, consisting of a names
     optionally followed by a typed value:

     name          typeless [boolean] capability name is present [true]
     nameTvalue    capability (name, T) has value value
     name@         no capability name exists
     nameT@        capability (name, T) does not exist

     Names consist of one or more characters.  Names may contain any character except `:', but it is usually
     best to restrict them to the printable characters and avoid use of graphics like `#', `=', `%', `@',
     etc.  Types are single characters used to separate capability names from their associated typed values.
     Types may be any character except a `:'.  Typically, graphics like `#', `=', `%', etc. are used.  Val-ues Values
     ues may be any number of characters and may contain any character except `:'.

CAPABILITY DATABASE SEMANTICS
     Capability records describe a set of (name, value) bindings.  Names may have multiple values bound to
     them.  Different values for a name are distinguished by their types.  The cgetcap() function will
     return a pointer to a value of a name given the capability name and the type of the value.

     The types `#' and `=' are conventionally used to denote numeric and string typed values, but no
     restriction on those types is enforced.  The functions cgetnum() and cgetstr() can be used to implement
     the traditional syntax and semantics of `#' and `='.  Typeless capabilities are typically used to
     denote boolean objects with presence or absence indicating truth and false values respectively.  This
     interpretation is conveniently represented by:

           (getcap(buf, name, ':') != NULL)

     A special capability, tc= name, is used to indicate that the record specified by name should be substi-tuted substituted
     tuted for the tc capability.  Tc capabilities may interpolate records which also contain tc capabili-ties capabilities
     ties and more than one tc capability may be used in a record.  A tc expansion scope (i.e., where the
     argument is searched for) contains the file in which the tc is declared and all subsequent files in the
     file array.

     When a database is searched for a capability record, the first matching record in the search is
     returned.  When a record is scanned for a capability, the first matching capability is returned; the
     capability :nameT@: will hide any following definition of a value of type T for name; and the capabil-ity capability
     ity :name@: will prevent any following values of name from being seen.

     These features combined with tc capabilities can be used to generate variations of other databases and
     records by either adding new capabilities, overriding definitions with new definitions, or hiding fol-lowing following
     lowing definitions via `@' capabilities.

EXAMPLES
           example|an example of binding multiple values to names:\
                :foo%bar:foo^blah:foo@:\
                :abc%xyz:abc^frap:abc$@:\
                :tc=more:

     The capability foo has two values bound to it (bar of type `%' and blah of type `^') and any other
     value bindings are hidden.  The capability abc also has two values bound but only a value of type `$'
     is prevented from being defined in the capability record more.

           file1:
                new|new_record|a modification of "old":\
                     :fript=bar:who-cares@:tc=old:blah:tc=extensions:
           file2:
                old|old_record|an old database record:\
                     :fript=foo:who-cares:glork#200:

     The records are extracted by calling cgetent() with file1 preceding file2.  In the capability record
     new in file1, fript=bar overrides the definition of fript=foo interpolated from the capability record
     old in file2, who-cares@ prevents the definition of any who-cares definitions in old from being seen,
     glork#200 is inherited from old, and blah and anything defined by the record extensions is added to
     those definitions in old.  Note that the position of the fript=bar and who-cares@ definitions before
     tc=old is important here.  If they were after, the definitions in old would take precedence.

CGETNUM AND CGETSTR SYNTAX AND SEMANTICS
     Two types are predefined by cgetnum() and cgetstr():

     name#number    numeric capability name has value number
     name=string    string capability name has value string
     name#@         the numeric capability name does not exist
     name=@         the string capability name does not exist

     Numeric capability values may be given in one of three numeric bases.  If the number starts with either
     `0x' or `0X' it is interpreted as a hexadecimal number (both upper and lower case a-f may be used to
     denote the extended hexadecimal digits).  Otherwise, if the number starts with a `0' it is interpreted
     as an octal number.  Otherwise the number is interpreted as a decimal number.

     String capability values may contain any character.  Non-printable ASCII codes, new lines, and colons
     may be conveniently represented by the use of escape sequences:

     ^X        ('X' & 037)          control-X
     \b, \B    (ASCII 010)          backspace
     \t, \T    (ASCII 011)          tab
     \n, \N    (ASCII 012)          line feed (newline)
     \f, \F    (ASCII 014)          form feed
     \r, \R    (ASCII 015)          carriage return
     \e, \E    (ASCII 027)          escape
     \c, \C    (:)                  colon
     \\        (\)                  back slash
     \^        (^)                  caret
     \nnn      (ASCII octal nnn)

     A `\' may be followed by up to three octal digits directly specifies the numeric code for a character.
     The use of ASCII NULs, while easily encoded, causes all sorts of problems and must be used with care
     since NULs are typically used to denote the end of strings; many applications use `\200' to represent a
     NUL.

DIAGNOSTICS
     The cgetent(), cgetset(), cgetmatch(), cgetnum(), cgetstr(), cgetustr(), cgetfirst(), and cgetnext()
     functions return a value greater than or equal to 0 on success and a value less than 0 on failure.  The
     cgetcap() function returns a character pointer on success and a NULL on failure.

     The cgetent(), and cgetset() functions may fail and set errno for any of the errors specified for the
     library functions: fopen(3), fclose(3), open(2), and close(2).

     The cgetent(), cgetset(), cgetstr(), and cgetustr() functions may fail and set errno as follows:

     [ENOMEM]           No memory to allocate.

SEE ALSO
     cap_mkdb(1), malloc(3)

BUGS
     Colons (`:') cannot be used in names, types, or values.

     There are no checks for tc=name loops in cgetent().

     The buffer added to the database by a call to cgetset() is not unique to the database but is rather
     prepended to any database used.

BSD                             March 22, 2002                             BSD

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