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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]
       [--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 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.

       Because	Unix  filenames	 can contain blanks and	newlines, this default
       behaviour is often problematic; filenames containing blanks and/or new-
       lines  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 message
       is issued on stderr when	this happens.

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

       --null
       -0     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).  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.

       --delimiter=delim
       -d delim
	      Input items are terminated by the	specified  character.	Quotes
	      and  backslash  are not special; every character in the input is
	      taken literally.	Disables  the  end-of-file  string,  which  is
	      treated  like any	other argument.	 This can be used when the in-
	      put consists of simply newline-separated items, although	it  is
	      almost  always better to design your program to use --null where
	      this is possible.	 The specified delimiter may be	a single char-
	      acter,  a	 C-style  character  escape such as \n,	or an octal or
	      hexadecimal escape code.	Octal and hexadecimal escape codes are
	      understood as for	the printf command.   Multibyte	characters are
	      not supported.

       -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 ig-
	      nored.  If neither -E nor	-e is used, no end of file  string  is
	      used.

       --eof[=eof-str]
       -e[eof-str]
	      This option is a synonym for the -E option.  Use -E instead, be-
	      cause 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.

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

       -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.

       --replace[=replace-str]
       -i[replace-str]
	      This  option  is	a  synonym for -Ireplace-str if	replace-str is
	      specified, and for -I{} otherwise.  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.

       --max-lines[=max-lines]
       -l[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.

       --max-args=max-args
       -n 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.

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

       --no-run-if-empty
       -r     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.

       --max-chars=max-chars
       -s 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 sys-
	      tem-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.

       --verbose
       -t     Print the	command	line on	the standard error output before  exe-
	      cuting it.

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

       --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.

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

       --max-procs=max-procs
       -P 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 with -P; otherwise chances  are  that
	      only one exec will be done.

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 ex-
       tra 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 Edi-
       tion) 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	porta-
       ble,  they  must	not rely on a larger value.  However, I	know of	no im-
       plementation whose actual limit is that small.  The  --show-limits  op-
       tion  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), Find-
       ing 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  al-
       ways  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  be-
       cause  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  encoun-
       ters  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  lim-
       it,  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://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 com-
       ments 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)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | SEE ALSO | BUGS

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