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XARGS(1)		    General Commands Manual		      XARGS(1)

NAME
       xargs - build and execute command lines from standard input

SYNOPSIS
       xargs [options] [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.

       The command line	for command is built up	until it reaches a  system-de-
       fined  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 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
       -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).  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.	Other-
	      wise, 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 charac-
	      ter 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.	  When
	      processing  the input, quotes and	backslash are not special; ev-
	      ery 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	possi-
	      ble.

       -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.

       -e[eof-str], --eof[=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.

       -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 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  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 increase	it above an  implemen-
	      tation-defined  limit  (which is shown with --show-limits).  You
	      cannot decrease it below 1.  xargs  never	 terminates  its  com-
	      mands; when asked	to decrease, it	merely waits for more than one
	      existing command to terminate before starting another.

	      Please note that it is up	to the called  processes  to  properly
	      manage  parallel	access	to  shared resources.  For example, if
	      more than	one of them tries to print to stdout, the output  will
	      be produced in an	indeterminate order (and very likely mixed up)
	      unless the processes collaborate in some way  to	prevent	 this.
	      Using  some  kind	 of  locking scheme is one way to prevent such
	      problems.	 In general, using a locking scheme will  help	ensure
	      correct  output  but  reduce  performance.  If you don't want to
	      tolerate the performance difference,  simply  arrange  for  each
	      process to produce a separate output file	(or otherwise use sep-
	      arate resources).

       -o, --open-tty
	      Reopen stdin as /dev/tty in the child process  before  executing
	      the  command.  This is useful if you want	xargs to run an	inter-
	      active application.

       -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 re-
	      sponse starts with `y' or	`Y'.  Implies -t.

       --process-slot-var=name
	      Set the environment variable name	to a unique value in each run-
	      ning  child process.  Values are reused once child processes ex-
	      it.  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 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.  xargs automatically adapts to tighter  con-
	      straints.

       --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  exe-
	      cuting 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.

       The  options  --max-lines  (-L,	-l), --replace (-I, -i)	and --max-args
       (-n) are	mutually exclusive. If some of them are	specified at the  same
       time,  then  xargs  will	generally use the option specified last	on the
       command line, i.e., it will reset the value  of	the  offending	option
       (given  before) to its default value.  Additionally, xargs will issue a
       warning diagnostic on stderr.  The exception to this rule is  that  the
       special	max-args value 1 ('-n1') is ignored after the --replace	option
       and its aliases -I and -i, because it would not actually	conflict.

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.

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 -o option is	an extension to	the POSIX standard for better compati-
       bility with BSD.

       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.

BUGS
       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 it never encounters a
       line which is longer than it can	handle.	  This is not an  ideal	 solu-
       tion.   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.

REPORTING BUGS
       GNU   findutils	 online	  help:	  <https://www.gnu.org/software/findu-
       tils/#get-help>
       Report any translation bugs to <https://translationproject.org/team/>

       Report any other	issue via the form at the GNU Savannah bug tracker:
	      <https://savannah.gnu.org/bugs/?group=findutils>
       General	topics	about  the  GNU	findutils package are discussed	at the
       bug-findutils mailing list:
	      <https://lists.gnu.org/mailman/listinfo/bug-findutils>

COPYRIGHT
       Copyright (C) 1990-2021 Free Software Foundation, Inc.  License GPLv3+:
       GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
       This  is	 free  software:  you  are free	to change and redistribute it.
       There is	NO WARRANTY, to	the extent permitted by	law.

SEE ALSO
       find(1),	kill(1), locate(1), updatedb(1),  fork(2),  execvp(3),	locat-
       edb(5), signal(7)

       Full documentation <https://www.gnu.org/software/findutils/xargs>
       or available locally via: info xargs

								      XARGS(1)

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

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