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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | SEE ALSO | BUGS | COLOPHON |
XARGS(1) General Commands Manual XARGS(1)
xargs - build and execute command lines from standard input
xargs [options] [command [initial-arguments]]
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.
-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.
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 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.
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.
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.
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.
This page is part of the findutils (find utilities) project.
Information about the project can be found at
⟨http://www.gnu.org/software/findutils/⟩. If you have a bug report
for this manual page, see ⟨http://www.gnu.org/software/findutils/⟩.
This page was obtained from the project's upstream Git repository
⟨git://git.savannah.gnu.org/findutils.git⟩ on 2017-07-05. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
XARGS(1)
Pages that refer to this page: dpkg-name(1), find(1), locate(1), updatedb(1), xargs(1), lsof(8)