Linux Commands Examples

A great documentation place for Linux commands


build and execute command lines from standard input

see also : find - locate - updatedb


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]]

add an example, a script, a trick and tips

: email address (won't be displayed)
: name

Step 2

Thanks for this example ! - It will be moderated and published shortly.

Feel free to post other examples
Oops ! There is a tiny cockup. A damn 404 cockup. Please contact the loosy team who maintains and develops this wonderful site by clicking in the mighty feedback button on the side of the page. Say what happened. Thanks!


echo -n host1 host2 host3 | xargs -d " " -i -n 1 -P 0 rsh {} -l username aplay soundtrack.wav

##What does it do ?

This launch a command simultaneously on many hosts, a bit like the parallel utility.
example added by webreac

Grep exits abnormally with code 123 when running rgrep on emacs

Looking at xargs exit code documentation:

123 if any invocation of the command exited with status 1-125

but according to grep documentation 1 is the exit status if grep didn't match the pattern

   Normally, the exit status is 0 if selected lines are found and 1 otherwise.  

So to me it seems that the command line that emacs uses to issue an 'rgrep' search will always return 123, and this error either needs to be suppressed or replaced with a command line such as

find . -type f \( -name \*.\[ch\] \) -exec grep -i -nH -e v4l

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 -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.

f $* |xargs mate

xargs --replace/-I for single arguments

You can echo with newlines to achieve your expected result. In your case with the server expansion that would be:

$ echo -e server{1..4}"\n" | xargs -I{} echo derp {}
derp server1
derp server2
derp server3
derp server4

Running find and xargs in background

If you want to run both in background, put them in a subshell:

(find /tmp/ -type f -mtime +3 | xargs rm -Rf) &

But, please, don't do this. Piping find output into xargs is unsafe unless you use the following options, which are supported in GNU and BSD find and xargs:

find … -print0 | xargs -0 …

If find returned files with spaces in their name you could – without even knowing – irreversibly delete the wrong folders. Carefully read the find manual and the section about deleting files for more info.

The safest way, in your case, would be:

find /tmp/ -type f -mtime +3 -delete &

Trying to understand xargs

The confusion is that wildcard characters such as * and *.* are evaluated by the shell when you type the command.

Therefore datafind/run*.* is evaluated by the shell and would be replaced by the filenames which match that, but it does not find any files that match. Therefore datafind/run*.* is given to the xargs command and then it passes that right through to the ls command.

The ls command does not understand wildcard characters so it just takes its input and tries to find a file with that name. There is no file with the name run*.* so you get an error No such file or directory.


How to use wildcards in a xargs-command?

Just don't use xargs for that. Use a for loop:

for i in $(seq 1 15); do
    mv ${i}_* $i

Even better is to use brace expansion instead of seq:

mkdir {1..15}

for i in {1..15}; do
    mv ${i}_* $i

rsync N newest files in a directory

Assuming you want to send files from the current working directory:

rsync `ls -tp | grep -v / | head -n <n>` <destination> <options>

will do the trick. For example:

rsync `ls -tp | grep -v / | head -n 10` user@host:/dest/dir/ --progress --compress

This will give an error if there are no files to be found in the current working directory, or if any of the top files contain spaces or other special characters.

The ` characters around ls -tp | grep -v / | head -n <n> tell bash to run the commands and replaced them with the resulting file list as a space separated list. The -t option tells ls to sort by timestamp, the -p tells it to add a / after directory names and the grep part screens out lines ending / so you don't end up sending directories over. Add -c to the ls options if you want the newest files to be judged by creation time instead of modification time (though note that some programs will remove and replace files instead of updating them so ctime and mtime can be the same even though a file seems to have been around longer).

I'll not claim it is without doubt the easiest way but it would be the way I'd first think of.


How do I use find to copy all found files to a new name in their same directories?

This solution is probably the most portable:

find "../content" -name "*_compressed.swf" -exec sh -c 'cp {} `dirname {}`/`basename {} compressed.swf`content.swf' \;

There is also the famous script which is distributed with Perl, and the rename command which could have made this a bit easier. These aren't available on all distributions though, these commands are for the most part.


Spawning multiple parallel wgets and storing results in a bash array to be pretty printed when all wgets are done

One trivial solution would be to log the output from each of the wget commands to a separate file and using cat to merge them afterwards.


Xargs string interpolation, not by inserting a space

find -name "*.html" | xargs -d"\n" -I"{}" touch ../template/{}

find -name "*.html" -exec touch ../template/{} \;

Note that find *.html is wrong, since wildcards are expanded before command execution.


Create symlinks recursively for a whole tree

cp -rs source/ dest/ should do the trick. The directory structure will be recreated at dest/ with each file being a symlink to its counterpart in source.


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.



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.



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.


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.


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.


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.


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.


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.


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.



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.



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.


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.



Print the command line on the standard error output before executing it.


Print the version number of xargs and exit.


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 if the size (see the -s option) is exceeded.


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.

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 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.


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 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[:dot:]org.

see also

find , locate , locatedb, updatedb , fork, execvp, Finding Files (on-line in Info, or printed)

How can this site be more helpful to YOU ?

give  feedback