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

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

SYNOPSIS
     xargs [-0oprt] [-E eofstr] [-I replstr [-R replacements] [-S replsize]] [-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 stan-
     dard input and executes utility with the strings as arguments.

     Any arguments specified on the command line are given to utility upon each invocation, fol-
     lowed by some number of the arguments read from the standard input of xargs.  This is
     repeated 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 charac-
     ters, excluding newlines, up to the matching single quote.  Double quotes escape all non-
     double quote characters, excluding newlines, 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 replsize (or 255 if no -S flag is specified) bytes; this
	     is implemented by concatenating as much of the argument containing replstr as possi-
	     ble, to the constructed arguments to utility, up to replsize bytes.  The size limit
	     does not apply to arguments to utility which do not contain replstr, and further-
	     more, 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 command(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.  Furthermore, 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 lines read.	If EOF is reached and fewer lines have
	     been read than number then utility will be called with the available lines.

     -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 argu-
	     ments 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
	     affirmative 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 terminal.

     -r      Compatibility with GNU xargs.  The GNU version of xargs runs the utility argument at
	     least once, even if xargs input is empty, and it supports a -r option to inhibit
	     this behavior.  The NetBSD version of xargs does not run the utility argument on
	     empty input, but it supports the -r option for command-line compatibility with GNU
	     xargs; but the -r option does nothing in the NetBSD version of xargs.

     -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 replsize
	     Specify the amount of space (in bytes) that -I can use for replacements.  The
	     default for replsize is 255.

     -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 (includ-
	     ing 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 invocation of utility exits with a value of 255.

FILES
     /dev/tty  used to read responses in prompt mode

EXIT STATUS
     xargs exits with one of the following values:
     0	     All invocations of utility returned a zero exit status.
     123     One or more invocations of utility returned a nonzero exit status.
     124     The utility exited with a 255 exit status.
     125     The utility was killed or stopped by a signal.
     126     The utility was found but could not be invoked.
     127     The utility could not be found.
     1	     Some other error occurred.

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

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

HISTORY
     The xargs utility appeared in PWB UNIX 1.0.  It made its first BSD appearance in the 4.3
     Reno release.

     The meaning of 123, 124, and 125 exit values and the -0 option were taken from GNU xargs.

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					December 21, 2010				      BSD
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