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XARGS(1)                  BSD General Commands Manual                 XARGS(1)

NAME
     xargs -- construct argument list(s) and execute utility

SYNOPSIS
     xargs [-0opt] [-E eofstr] [-I replstr [-R replacements]] [-J replstr] [-L number] [-n number [-x]]
           [-P maxprocs] [-s size] [utility [argument ...]]

DESCRIPTION
     The xargs utility reads space, tab, newline and end-of-file delimited strings from the standard input
     and executes utility with the strings as arguments.

     Any arguments specified on the command line are given to utility upon each invocation, followed by some
     number of the arguments read from the standard input of xargs.  The utility is repeatedly executed
     until standard input is exhausted.

     Spaces, tabs and newlines may be embedded in arguments using single (`` ' '') or double (``"'') quotes
     or backslashes (``\'').  Single quotes escape all non-single quote characters, excluding newlines, up
     to the matching single quote.  Double quotes escape all non-double quote characters, excluding new-lines, newlines,
     lines, up to the matching double quote.  Any single character, including newlines, may be escaped by a
     backslash.

     The options are as follows:

     -0      Change xargs to expect NUL (``\0'') characters as separators, instead of spaces and newlines.
             This is expected to be used in concert with the -print0 function in find(1).

     -E eofstr
             Use eofstr as a logical EOF marker.

     -I replstr
             Execute utility for each input line, replacing one or more occurrences of replstr in up to
             replacements (or 5 if no -R flag is specified) arguments to utility with the entire line of
             input.  The resulting arguments, after replacement is done, will not be allowed to grow beyond
             255 bytes; this is implemented by concatenating as much of the argument containing replstr as
             possible, to the constructed arguments to utility, up to 255 bytes.  The 255 byte limit does
             not apply to arguments to utility which do not contain replstr, and furthermore, no replacement
             will be done on utility itself.  Implies -x.

     -J replstr
             If this option is specified, xargs will use the data read from standard input to replace the
             first occurrence of replstr instead of appending that data after all other arguments.  This
             option will not affect how many arguments will be read from input (-n), or the size of the com-mand(s) command(s)
             mand(s) xargs will generate (-s).  The option just moves where those arguments will be placed
             in the command(s) that are executed.  The replstr must show up as a distinct argument to xargs.
             It will not be recognized if, for instance, it is in the middle of a quoted string.  Further-more, Furthermore,
             more, only the first occurrence of the replstr will be replaced.  For example, the following
             command will copy the list of files and directories which start with an uppercase letter in the
             current directory to destdir:

                   /bin/ls -1d [A-Z]* | xargs -J % cp -rp % destdir

     -L number
             Call utility for every number non-empty lines read.  A line ending with a space continues to
             the next non-empty line.  If EOF is reached and fewer lines have been read than number then
             utility will be called with the available lines.  The -L and -n options are mutually-exclusive;
             the last one given will be used.

     -n number
             Set the maximum number of arguments taken from standard input for each invocation of utility.
             An invocation of utility will use less than number standard input arguments if the number of
             bytes accumulated (see the -s option) exceeds the specified size or there are fewer than number
             arguments remaining for the last invocation of utility.  The current default value for number
             is 5000.

     -o      Reopen stdin as /dev/tty in the child process before executing the command.  This is useful if
             you want xargs to run an interactive application.

     -P maxprocs
             Parallel mode: run at most maxprocs invocations of utility at once.

     -p      Echo each command to be executed and ask the user whether it should be executed.  An affirma-tive affirmative
             tive response, `y' in the POSIX locale, causes the command to be executed, any other response
             causes it to be skipped.  No commands are executed if the process is not attached to a termi-nal. terminal.
             nal.

     -R replacements
             Specify the maximum number of arguments that -I will do replacement in.  If replacements is
             negative, the number of arguments in which to replace is unbounded.

     -s size
             Set the maximum number of bytes for the command line length provided to utility.  The sum of
             the length of the utility name, the arguments passed to utility (including NULL terminators)
             and the current environment will be less than or equal to this number.  The current default
             value for size is ARG_MAX - 4096.

     -t      Echo the command to be executed to standard error immediately before it is executed.

     -x      Force xargs to terminate immediately if a command line containing number arguments will not fit
             in the specified (or default) command line length.

     If utility is omitted, echo(1) is used.

     Undefined behavior may occur if utility reads from the standard input.

     The xargs utility exits immediately (without processing any further input) if a command line cannot be
     assembled, utility cannot be invoked, an invocation of utility is terminated by a signal, or an invoca-tion invocation
     tion of utility exits with a value of 255.

LEGACY DESCRIPTION
     In legacy mode, the -L option treats all newlines as end-of-line, regardless of whether the line is
     empty or ends with a space.  In addition, the -L and -n options are not mutually-exclusive.

     For more information about legacy mode, see compat(5).

EXIT STATUS
     The xargs utility exits with a value of 0 if no error occurs.  If utility cannot be found, xargs exits
     with a value of 127, otherwise if utility cannot be executed, xargs exits with a value of 126.  If any
     other error occurs, xargs exits with a value of 1.

SEE ALSO
     echo(1), find(1), execvp(3), compat(5)

STANDARDS
     The xargs utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compliant.  The -J, -o, -P and -R
     options are non-standard FreeBSD extensions which may not be available on other operating systems.

HISTORY
     The xargs command appeared in PWB UNIX.

BUGS
     If utility attempts to invoke another command such that the number of arguments or the size of the
     environment is increased, it risks execvp(3) failing with E2BIG.

     The xargs utility does not take multibyte characters into account when performing string comparisons
     for the -I and -J options, which may lead to incorrect results in some locales.

BSD                             August 2, 2004                             BSD

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