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-
       defined 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
       executed 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
       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.

       -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.
              Otherwise, 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
              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.
              When processing the input, quotes and backslash are not special;
              every 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

       -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

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

       -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
              implementation-defined limit (which is shown with --show-
              limits).  You cannot decrease it below 1.  xargs never
              terminates its commands; when asked to decrease, it merely waits
              for more than one existing command to terminate before starting

              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
              separate 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
              response starts with `y' or `Y'.  Implies -t.

              Set the environment variable name to a unique value in each
              running child process.  Values are reused once child processes
              exit.  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
              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.  xargs automatically adapts to tighter

              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
              executing 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
       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.

       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
       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.

       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
       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

       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-request@gnu.org.