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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  com-
       mand  (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 newlines 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.  Otherwise, 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  backslash-
              es.  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 input 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  de-
              limiter may be a single character, a C-style character escape such as \n, or an octal or hexadecimal es-
              cape 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 ignored.  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, because 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  speci-
              fied, 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 response 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 system-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 executing 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 containing 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 containing 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 extra 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 Edition) 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 portable, they
       must not rely on a larger value.  However, I know of no implementation whose actual limit is that  small.   The
       --show-limits option 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), Finding 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 always 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 because 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  encounters  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 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.

       The  best  way to report a bug is to use the form at http://savannah.gnu.org/bugs/?group=findutils.  The reason
       for this is that you will then be able to track progress in fixing the problem.   Other comments 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-requestATgnu.org.



                                                                      XARGS(1)