XARGS(1)						      General Commands Manual							  XARGS(1)

NAME

       xargs - build and execute command lines from standard input

SYNOPSIS

       xargs  [-0prtx]	[-E eof-str] [-e[eof-str]] [--eof[=eof-str]] [--null] [-d delimiter] [--delimiter delimiter] [-I replace-str] [-i[replace-
       str]] [--replace[=replace-str]] [-l[max-lines]] [-L max-lines] [--max-lines[=max-lines]] [-n max-args] [--max-args=max-args] [-s max-chars]
       [--max-chars=max-chars]	 [-P   max-procs]   [--max-procs=max-procs]   [--process-slot-var=name]   [--interactive]   [--verbose]   [--exit]
       [--no-run-if-empty] [--arg-file=file] [--show-limits] [--version] [--help] [command [initial-arguments]]

DESCRIPTION

       This manual page documents the GNU version of xargs.  xargs reads items from the standard input, delimited by blanks (which can be protect-
       ed  with  double  or  single quotes or a backslash) or newlines, and executes the command (default is /bin/echo) one or more times with any
       initial-arguments followed by items read from standard input.  Blank lines on the standard input are ignored.

       The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are  used).   The  specified
       command	will be invoked as many times as necessary to use up the list of input items.  In general, there will be many fewer invocations of
       command than there were items in the input.  This will normally have significant performance benefits.  Some commands can usefully be  exe-
       cuted in parallel too; see the -P option.

       Because	Unix  filenames  can  contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or
       newlines are incorrectly processed by xargs.  In these situations it is better to use the -0 option, which prevents such  problems.    When
       using  this  option  you will need to ensure that the program which produces the input for xargs also uses a null character as a separator.
       If that program is GNU find for example, the -print0 option does this for you.

       If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input.  An error  mes-
       sage is issued on stderr when this happens.

OPTIONS

       -0, --null
	      Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every charac-
	      ter is taken literally).	Disables the end of file string, which is treated like any other argument.  Useful when input items  might
	      contain white space, quote marks, or backslashes.  The GNU find -print0 option produces input suitable for this mode.

       -a file, --arg-file=file
	      Read  items from file instead of standard input.	If you use this option, stdin remains unchanged when commands are run.	Otherwise,
	      stdin is redirected from /dev/null.

       --delimiter=delim, -d delim
	      Input items are terminated by the specified character.  The specified delimiter may be a single character, a C-style  character  es-
	      cape  such  as 
, or an octal or hexadecimal escape code.  Octal and hexadecimal escape codes are understood as for the printf com-
	      mand.   Multibyte characters are not supported.  When processing the input, quotes and backslash are not special; every character in
	      the input is taken literally.  The -d option disables any end-of-file string, which is treated like any other argument.  You can use
	      this option when the input consists of simply newline-separated items, although it is almost always better to design your program to
	      use --null where this is possible.

       -E eof-str
	      Set  the	end of file string to eof-str.	If the end of file string occurs as a line of input, the rest of the input is ignored.	If
	      neither -E nor -e is used, no end of file string is used.

       -e [eof-str], --eof[=eof-str]
	      This option is a synonym for the -E option.  Use -E instead, because it is POSIX compliant while this option is not.  If eof-str	is
	      omitted, there is no end of file string.	If neither -E nor -e is used, no end of file string is used.

       -I replace-str
	      Replace  occurrences of replace-str in the initial-arguments with names read from standard input.  Also, unquoted blanks do not ter-
	      minate input items; instead the separator is the newline character.  Implies -x and -L 1.

       -i [replace-str], --replace[=replace-str]
	      This option is a synonym for -Ireplace-str if replace-str is specified.  If the replace-str argument is missing, the effect  is  the
	      same as -I{}.  This option is deprecated; use -I instead.

       -L max-lines
	      Use  at  most max-lines nonblank input lines per command line.  Trailing blanks cause an input line to be logically continued on the
	      next input line.	Implies -x.

       -l [max-lines], --max-lines[=max-lines]
	      Synonym for the -L option.  Unlike -L, the max-lines argument is optional.  If max-lines is not specified, it defaults to one.   The
	      -l option is deprecated since the POSIX standard specifies -L instead.

       -n max-args, --max-args=max-args
	      Use  at most max-args arguments per command line.  Fewer than max-args arguments will be used if the size (see the -s option) is ex-
	      ceeded, unless the -x option is given, in which case xargs will exit.

       -P max-procs, --max-procs=max-procs
	      Run up to max-procs processes at a time; the default is 1.  If max-procs is 0, xargs will run as many processes  as  possible  at  a
	      time.   Use  the -n option or the -L option with -P; otherwise chances are that only one exec will be done.  While xargs is running,
	      you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a	SIGUSR2  to  decrease  the
	      number.  You cannot decrease it below 1.	xargs never terminates its commands; when asked to decrease, it merely waits for more than
	      one existing command to terminate before starting another.

       -p, --interactive
	      Prompt the user about whether to run each command line and read a line from the terminal.  Only run the command line if the response
	      starts with `y' or `Y'.  Implies -t.

       --process-slot-var=name
	      Set  the	environment  variable  name to a unique value in each running child process.  Values are reused once child processes exit.
	      This can be used in a rudimentary load distribution scheme, for example.

       -r, --no-run-if-empty
	      If the standard input does not contain any nonblanks, do not run the command.  Normally, the command is run once even if there is no
	      input.  This option is a GNU extension.

       -s max-chars, --max-chars=max-chars
	      Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends
	      of the argument strings.	The largest allowed value is system-dependent, and is calculated as the argument length  limit	for  exec,
	      less  the  size  of your environment, less 2048 bytes of headroom.  If this value is more than 128KiB, 128Kib is used as the default
	      value; otherwise, the default value is the maximum.  1KiB is 1024 bytes.	xargs automatically adapts to tighter constraints.

       --show-limits
	      Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s op-
	      tion.  Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything.

       -t, --verbose
	      Print the command line on the standard error output before executing it.

       -x, --exit
	      Exit if the size (see the -s option) is exceeded.

       --help Print a summary of the options to xargs and exit.

       --version
	      Print the version number of xargs and exit.

EXAMPLES

       find /tmp -name core -type f -print | xargs /bin/rm -f

       Find files named core in or below the directory /tmp and delete them.  Note that this will work incorrectly if there are any filenames con-
       taining newlines or spaces.

       find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f

       Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names  con-
       taining spaces or newlines are correctly handled.

       find /tmp -depth -name core -type f -delete

       Find  files  named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid
       the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process).

       cut -d: -f1 < /etc/passwd | sort | xargs echo

       Generates a compact listing of all the users on the system.

       xargs sh -c 'emacs "$@" < /dev/tty' emacs

       Launches the minimum number of copies of Emacs needed, one after the other, to edit the files listed on xargs' standard input.  This  exam-
       ple achieves the same effect as BSD's -o option, but in a more flexible and portable way.

EXIT STATUS

       xargs exits with the following status:
       0 if it succeeds
       123 if any invocation of the command exited with status 1-125
       124 if the command exited with status 255
       125 if the command is killed by a signal
       126 if the command cannot be run
       127 if the command is not found
       1 if some other error occurred.

       Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal.

STANDARDS CONFORMANCE

       As  of  GNU  xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker.  POSIX (IEEE Std 1003.1, 2004
       Edition) allows this.

       The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the  standard.	 Therefore
       you should use -L and -I instead, respectively.

       The  POSIX  standard  allows implementations to have a limit on the size of arguments to the exec functions.  This limit could be as low as
       4096 bytes including the size of the environment.  For scripts to be portable, they must not rely on a larger value.  However, I know of no
       implementation  whose  actual limit is that small.  The --show-limits option can be used to discover the actual limits in force on the cur-
       rent system.

SEE ALSO

       find(1), locate(1), locatedb(5), updatedb(1), fork(2), execvp(3), kill(1), signal(7), Finding Files (on-line in Info, or printed)

BUGS

       The -L option is incompatible with the -I option, but perhaps should not be.

       It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of  input  files
       and  their use in the commands that xargs issues.  If other users have access to the system, they can manipulate the filesystem during this
       time window to force the action of the commands xargs runs to apply to files that you didn't intend.  For a  more  detailed  discussion	of
       this  and  related  problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation.  The -execdir
       option of find can often be used as a more secure alternative.

       When you use the -I option, each line read from the input is buffered internally.   This means that there is an upper limit on  the  length
       of  input  line that xargs will accept when used with the -I option.  To work around this limitation, you can use the -s option to increase
       the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not  occur.
       For example:

       somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}'

       Here,  the  first  invocation of xargs has no input line length limit because it doesn't use the -i option.  The second invocation of xargs
       does have such a limit, but we have ensured that the it never encounters a line which is longer than it can handle.   This is not an  ideal
       solution.   Instead,  the  -i  option should not impose a line length limit, which is why this discussion appears in the BUGS section.  The
       problem doesn't occur with the output of find(1) because it emits just one filename per line.

       The best way to report a bug is to use the form at http://savannah.gnu.org/bugs/?group=findutils.  The reason for this  is  that  you  will
       then  be  able  to  track progress in fixing the problem.   Other comments about xargs(1) and about the findutils package in general can be
       sent to the bug-findutils mailing list.	To join the list, send email to bug-findutils-request@gnu.org.

																	  XARGS(1)