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Updated: Wednesday, February 9, 2022

xargs (1g)


xargs - build and execute command lines from standard input


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]]


XARGS(1)                    General Commands Manual                   XARGS(1)

       xargs - build and execute command lines from standard input

       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]]

       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.

       -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

       -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-

       -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

       -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 ouptut 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).

       -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.

              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-

              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.

              Print the version number of xargs and exit.

       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.

       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.

       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

       See attributes(7) for descriptions of the following attributes:

       |Availability   | file/gnu-findutils |
       |Stability      | Uncommitted        |

       find(1),   locate(1),  locatedb(5),  updatedb(1),  fork(2),  execvp(3),
       kill(1), signal(7),

       The  full documentation for xargs is maintained as  a  Texinfo  manual.
       If the info and xargs programs are properly installed at your site, the
       command info xargs should give you access to the complete manual.

       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

       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.

       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This software was built from source available at https://github.com/or-
       acle/solaris-userland.  The original community  source  was  downloaded
       from  http://ftp.gnu.org/gnu/findutils/findutils-4.6.0.tar.gz.

       Further information about this software can be found on the open source
       community website at https://www.gnu.org/software/findutils.