Linux: Harnessing The Über-Powerful Find Command (+xargs)

you should mention how to redirect the permission denied messages

find / -name required 2> /dev/null

It might also be good to mention the standard technique for using find with tar.

find . -daystart -mtime 0 > temp tar -cvf stuff.tar -T temp rm temp

Generally you don’t want to use xargs with tar and the create (c) flag, unless your sure that there are only a very few files.

Excellent stuf!

I don’t think the following command-line from your article:

# Clean the images off of your *nix desktop
find ~/Desktop -name "*.jpg" -o -name "*.gif" -o -name "*.png" -print0 | xargs -0 mv ~/Pictures 

will work as you expect. You’ll want to wrap the find(1) -name tests in parentheses, otherwise you’ll only list the *.png files.

Also, the mv(1) command(s) that xargs(1) will generate, won’t work because the last argument needs to be a directory. Assuming your Desktop directory looks like this:

$ ls Desktop Pictures
Desktop:
bar.png  foo.gif  one.png  three.jpg  two.jpg

Pictures:

here’s the results of running your original command-line:

$ find Desktop  -name "*.jpg" -o -name "*.gif" -o -name "*.png"  -print0 | xargs -0 -t mv Pictures
mv Pictures Desktop/bar.png Desktop/one.png 
mv: when moving multiple files, last argument must be a directory
Try `mv --help' for more information.

Here’s a version that will work as you expect:

$ find Desktop  \( -name "*.jpg" -o -name "*.gif" -o -name "*.png" \) -print0 | xargs -0 -t mv --target-directory=Pictures
mv --target-directory=Pictures Desktop/three.jpg Desktop/two.jpg Desktop/foo.gif Desktop/bar.png Desktop/one.png

$ ls Desktop Pictures
Desktop:

Pictures:
bar.png  foo.gif  one.png  three.jpg  two.jpg

IIRC the –target-directory option is specific to the GNU version of mv(1).

If you had a standard mv(1) command lacking the –target-directory option, you’d need to move one file at a time and xargs wouldn’t provide much benefit over the -exec feature of find(1):

$ find Desktop  \( -name "*.jpg" -o -name "*.gif" -o -name "*.png" \) -print0 |  xargs -0 -t -i mv {} Pictures
mv Desktop/three.jpg Pictures
mv Desktop/two.jpg Pictures
mv Desktop/foo.gif Pictures
mv Desktop/bar.png Pictures
mv Desktop/one.png Pictures

$ ls Desktop Pictures
Desktop:

Pictures:
bar.png  foo.gif  one.png  three.jpg  two.jpg

The -t option to xargs(1) is your friend. It traces the commands generated by xargs(1). If you want to be extra cautious, use -p instead and it will print each command-line and ask you if you want to proceed.