Provided by: findutils_4.6.0+git+20180808-2_amd64 bug

NAME

       xargs - build and execute command lines from standard input

SYNOPSIS

       xargs [options] [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-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.

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.   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 possible.

       -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.

       -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 another.

              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 output 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).

       -o, --open-tty
              Reopen  stdin  as /dev/tty in the child process before executing the command.  This
              is useful if you want xargs to run an interactive application.

       -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.

       --process-slot-var=name
              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 constraints.

       --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 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.

       --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 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.

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 -o option is an extension to the POSIX standard for better compatibility with BSD.

       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), 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.

COPYRIGHT

       Copyright © 1990-2018 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or
       later <https://gnu.org/licenses/gpl.html>.
       This  is free software: you are free to change and redistribute it.  There is NO WARRANTY,
       to the extent permitted by law.

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
       https://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)