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 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
       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 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 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  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.

       -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 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
              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-request@gnu.org.

                                                                                                                                      XARGS(1)
 

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