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xargs


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]
       [--process-slot-var=name]    [--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.

       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-
              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 decrease it below 1.  xargs

       -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.


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,
       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),
       kill(1), signal(7), 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  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
       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)
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