Information about Xargs

xargs is a command of the Unix and most Unix-like operating systems. It becomes useful when you want to pass a large amount of arguments to a command. In that case xargs will break the list of arguments in sublists large enough to be acceptable (the reader should note that you can't pass arbitrary long lists of parameters to a command ^[1]).

For example commands like this:

rm /path/*

or this

rm `find /path -type f`

...will fail with an error message of "Argument list too long" if there are too many files in /path

However the version below (functionally equivalent with rm `find /path -type f`) will not fail:

find /path -type f -print0 | xargs -0 rm

In this example, find feeds the input of xargs with a long list of file names. xargs then splits this list in sublists and calls rm once for every sublist. Note that this is more efficient than the functionally equivalent version bellow:

find /path -type f -exec rm '{}' \;

...which would call rm once for every single file.

xargs often covers the same functionality as the backquote feature of many shells, but is more flexible and often also safer, especially if there are blanks or special characters in the input. It is a perfect companion for commands that output long lists of files like find, locate and grep.

Examples

find . -name "*.foo" | xargs grep bar does the same as grep bar `find . -name "*.foo"` Note that the preceding command uses backticks (`), not single quotes ('). It searches in all files in the current directory and its subdirectories which end in .foo for occurrences of the string bar. These commands will not work as expected if there are whitespace characters, including newlines, in the filenames. In order to avoid this limitation one may use:

find . -name "*.foo" -print0 | xargs -0 grep bar

...which uses GNU specific extensions to find and xargs to separate filenames using the null character;

find . -name "*.foo" -print0 | xargs -0 -t -r vi is similar to above, but launches the vi editor for each of the files. The -t prints the command to stderr before issuing it. The -r is a GNU extension that tells xargs not to run the command if no input was received.

find . -name "*.foo" -print0 | xargs -0 -i mv {} /tmp/trash uses -i to tell xargs to replace {} with the argument list

References

External links

• GNU man page on xargs

•  • [ e] Unix command line programs and builtins (more)
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