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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]
       [--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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