Thursday, March 13, 2008

Using xargs

I'm a big fan of the xargs command. It's widely used in shell scripts but not so much on the command line. It's a really handy command when you want to take an incoming argument and apply a command to it. Here's an example that would kill every process matching a given pattern of "firefox" (similar to killall).

ps aux | grep firefox | awk '{print $2}' | xargs kill -9

remove files matching *lock*:

ls *lock* | xargs rm

for more complex commands, you can set the incoming data to be stored in a token:

ls *lock* | xargs -I $ ls -l $


ls *lock | xargs -I {} ls -l {}

Obviously the possibilities go far beyond what's shown here. Play around with it.


Felipe said...

> ls *lock* | xargs rm
rm *lock*

That was easy ;-)

Gniourf said...

This is all wrong!!! NEVER, EVER parse the output of ls. ls' output is not meant to be parsed!!!

For example, try this:
# Create test files (with a space in the name)
touch hello\ {1..10}.lock
# try your stupid command: Surprise...
ls *lock* | xargs rm

Most of the time you'll be fine if you leave xargs alone (i.e., do not use xargs, there's always a better way to do it --- especially if your method involves parsing the output of some other program).

Dude, I like your vim tips better.

Petr said...

It is strange to know that output is not meant to be parsed for probably most often user _UNIX_ command.

ls -1 *lock* | sed -e "s/\(.\+\)/'\1'/" | xargs rm

or, if one decides to read man ls:

ls -1Q *lock* | xargs rm