XARGS(1) - phpMan

Command: man perldoc info search(apropos)  


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 pro-
       cessed by xargs.  In these situations it is better to use the -0 option, which pre-
       vents such problems.   When using this option you will need to ensure that the pro-
       gram  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  imme-
       diately  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 redi-
              rected 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 literal-
              ly).  Disables the end of file string, which is treated like any other argu-
              ment.   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  depre-
              cated 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 argu-
              ments 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 com-
              mand.  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 oper-
              ating system, xargs' choice of buffer size and the -s option.  Pipe the  in-
              put 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 op-
              tion 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  ef-
       ficiently  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 log-
       ical 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 in-
       stead, 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 cur-
       rent 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://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 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 AT gnu.org.



                                                                      XARGS(1)

Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2017-12-13 03:27 @127.0.0.1 CrawledBy CCBot/2.0 (http://commoncrawl.org/faq/)
Valid XHTML 1.0!Valid CSS!