Rename numbered files

Sometimes you have a bunch of files, for example a bunch of images, which name consists of just a number and an extension. When you want to process them further sorting them will sometimes fail when they are not prefixed with a zero. That’s easily solved in a one-liner

Under *nix systems the files are easily renamed to contain a prefix. The trick to do this is using printf and specifying a format. Below an one-liner, which exactly does that using the Bash shell.

for i in $(seq 20);do j=$(printf "%.3d" $i);mv $i.jpg $j.jpg;done

The for loop will run from 1 – 20 and renames (moves) the file from it’s original name to one with a prefix to make the number always use 3 positions.

So a list of files that consists of:

Pulsar:~$> ls
1.jpg	10.jpg	11.jpg	12.jpg	13.jpg	14.jpg	15.jpg	16.jpg	17.jpg	18.jpg	19.jpg	2.jpg	20.jpg	3.jpg	4.jpg	5.jpg	6.jpg	7.jpg	8.jpg	9.jpg
Pulsar:~$>

Becomes after running the command:

Pulsar:~$> ls
001.jpg	002.jpg	003.jpg	004.jpg	005.jpg	006.jpg	007.jpg	008.jpg	009.jpg	010.jpg	011.jpg	012.jpg	013.jpg	014.jpg	015.jpg	016.jpg	017.jpg	018.jpg	019.jpg	020.jpg
Pulsar:~$> 

And all of that in just one line 😉