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)
