XARGS

Section: User Commands (1)
Updated: 202-0-03
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NAME

xargs - build and execute command lines from standard input  

SYNOPSIS

xargs [option  ...] [command] [initia-argument  ...]  

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 echo) one or more times with any initia-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 syste-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 standard error 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 en-o-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find (and from POSIX Issue 8, IEEE Std 1003.1, 2024) -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, standard input remains unchanged when commands are run. Otherwise, standard input 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 -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 en-o-file string, which is treated like any other argument. You can use this option when the input consists of simply newlin-separated items, although it is almost always better to design your program to use --null where this is possible.

-E  eo-str

Set the en-o-file string to eo-str. If the en-o-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no en-o-file string is used. Other implementations of xargs may have a default logical en-o-file string, so if you want to portably ensure that no logical en-o-file string is in use, use -E [dq][dq] to disable the logical en-o-file string. See also STANDARDS CONFORMANCE.

-e[eo-str]

--eof[=eo-str]

This option is a synonym for the -E option. Use -E instead, because it is still POSI-compliant whereas the -e option was removed from the POSIX standard (IEEE Std 1003.1, 2004 Edition).

-I  replac-str

Replace occurrences of replac-str in the initia-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[replac-str]

--replace[=replac-str]

This option is a synonym for -Ireplac-str if replac-str is specified. If the replac-str argument is missing, the effect is the same as ``-I{} ''. The -i option was removed from the POSIX standard (IEEE Std 1003.1, 2004 Edition). Use -I instead.

-L  ma-lines

Use at most ma-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[ma-lines]

--max-lines[=ma-lines]

Synonym for the -L option. Unlike -L, the ma-lines argument is optional. If ma-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead.

-n  ma-args

--max-args=ma-args

Use at most ma-args arguments per command line. Fewer than ma-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  ma-procs

--max-procs=ma-procs

Run up to ma-procs processes at a time; the default is 1. If ma-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 implementatio-defined limit (which is shown with --sho-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. xargs always waits for all child processes to exit before exiting itself (but see BUGS).

If you do not use the -P option, xargs will not handle the SIGUSR1 and SIGUSR2 signals, meaning that they will terminate the program (unless they were blocked in the parent process before xargs was started).

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 standard output, 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 standard input 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.

-s  ma-chars

--max-chars=ma-chars

Use at most ma-chars characters per command line, including the command and initia-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is syste-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 128  KiB, 128  KiB is used as the default value; otherwise, the default value is the maximum. 1  KiB is 1024 bytes. xargs automatically adapts to tighter constraints.

--show-limits

Display the limits on the comman-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 --n-ru-i-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.

--

Delimit the option list. Later arguments, if any, are treated as operands even if they begin with ``-''. For example, ``xargs -- --help '' runs the command --help (found in PATH) instead of printing the usage text, and ``xargs -- --mycommand '' runs the command --mycommand instead of rejecting this as unrecognized option.

--help

Print a summary of the options to xargs and exit.

--version

Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i), and --max-args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on standard error. The exception to this rule is that the special ma-args value ``1'' (as in ``-n1 '') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict.

 

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 (and any commands run by xargs, if there were any, exited normally with exit status 0).

123

if any invocation of the command exited with status other than 0 or 255 (though see below).

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.

It is possible that future versions of xargs may exit with a status in the range 1-125 when the command it launched fails in some specific way not listed above. Nevertheless, xargs will comply with POSIX. The STANDARDS CONFORMANCE section explains the POSIX rules about the exit status of xargs. The commands run by xargs are run directly (with execvp(2)) rather than being invoked via the shell. The shell's (128 + signal) convention for reporting that a process had been killed by a signal is not used by xargs.  

STANDARDS CONFORMANCE

This section describes the relationship between GNU xargs and the standards with which it complies. Some portability considerations are mentioned.  

OPTIONS

Options specified in IEEE Std 1003.1, 2024 are -E, -I, -L, -n, -p, -r, -s, -t, -x and -0.

-E

Since findutils 4.2.9 (2004), GNU xargs has had no default logical en-o-file string. This may not be true of other implementations, so you should use -E [dq][dq] to be certain.

-e

Removed from POSIX in IEEE Std 1003.1, 2004. GNU xargs still supports this, but you should use -E instead.

-i

Removed from POSIX in IEEE Std 1003.1, 2004. GNU xargs still supports this but you should use -I instead.

-l

Removed from POSIX in IEEE Std 1003.1, 2004. GNU xargs still supports this but you should use -L instead.

-o

An extension to the POSIX standard for better compatibility with BSD. Not in POSIX.

-p

A GNU extension since before 1994. Added to POSIX in IEEE Std 1003.1, 2004.

-r

A GNU extension since before 1994. Added to POSIX in IEEE Std 1003.1, 2024.

-0

A GNU extension since before 1994. Added to POSIX in IEEE Std 1003.1, 2024.

 

EXEC SYSTEM CALL LIMITS

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.  

POSIX EXIT STATUS REQUIREMENTS

The POSIX standard specifies that certain kinds of problem must result in particular xargs return values. The table below summarizes how these requirements relate to the values listed in the EXIT STATUS section.

POSIX requirement GNU xargs behavior Situation Exit status Exit status Details Utility not found 127     127     execvp(2) failed with errno value ENOENT Utility could not be invoked 126     126     execvp(2) failed with any other error Any other no-success case 1- 125     125     Utility killed by a fatal signal 124     Utility exited with status 255 123     Utility exited with a status other than 0 or 255 2- 122     May be used in the future 1     Any other kind of error (such as a usage error) Successful completion 0     0

 

CONFORMANCE BUGS

Introduced	Fixed	Description
4.5.10 (2011)	4.10.0 (2024)	SIGUSR1 should be a fatal signal by default, but SIGUSR1 would not kill xargs even if the option was not in use.

 

HISTORY

The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, chapter ``Finding Files'', for more information.  

BUGS

 

SECURITY

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.  

IMPLEMENTATION LIMITS

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 [dq]{}[dq] -s 100000 rm [dq]{}[dq] 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 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.  

REPORTING BUGS

GNU findutils online help: <https://www.gnu.org/software/findutils/#ge-help>
Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker:

<https://savannah.gnu.org/bugs/?group=findutils>

General topics about the GNU findutils package are discussed at the bug-findutils mailing list:

<https://lists.gnu.org/mailman/listinfo/bu-findutils>

 

COPYRIGHT

Copyright © 1990-2026 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.  

SEE ALSO

find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs>
or available locally via: info xargs

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Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

EXIT STATUS

STANDARDS CONFORMANCE

OPTIONS

EXEC SYSTEM CALL LIMITS

POSIX EXIT STATUS REQUIREMENTS

CONFORMANCE BUGS

HISTORY

BUGS

SECURITY

IMPLEMENTATION LIMITS

REPORTING BUGS

COPYRIGHT

SEE ALSO