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XARGS(1)										 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 protected with double or single quotes or a back-
       slash) 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 invoca-
       tions  of command than there were items in the input.  This will normally have significant
       performance benefits.  Some commands can usefully be executed 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 prob-
       lems.   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 message is issued on stderr when this hap-
       pens.

OPTIONS
       -0, --null
	      Input items are terminated by a null character instead of by  whitespace,  and  the
	      quotes  and  backslash  are not special (every character is taken literally).  Dis-
	      ables 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  re-
	      mains  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 escape such as \n, or an octal or hexa-
	      decimal escape code.  Octal and hexadecimal escape codes are understood as for  the
	      printf  command.	 Multibyte characters are not supported.  When processing the in-
	      put, 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 new-
	      line-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 terminate 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 re-
	      place-str argument is missing, the effect is the same as -I{}.  This option is dep-
	      recated; 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 exceeded, 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 an-
	      other.

       -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'.  Im-
	      plies -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.  Nor-
	      mally, the command is run once even if there is no input.  This option is a GNU ex-
	      tension.

       -s max-chars, --max-chars=max-chars
	      Use at most max-chars characters per command line, including the command	and  ini-
	      tial-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 option.  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 containing 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 containing 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 example 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, respec-
       tively.

       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 envi-
       ronment.  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 current 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 dur-
       ing 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 in-
       crease the amount of buffer space that xargs uses, and you can also use an  extra  invoca-
       tion 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 out-
       put 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://savan-
       nah.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 findu-
       tils  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)
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