Provided by: findutils_4.4.0-2ubuntu3_i386 bug

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 -cemacs "$@" < /dev/ttyemacs

       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 stadard 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)