Ttyjfyk

I have a number of png and jpg files whose names are numbers, e.g.0100.png, in a directory,

• How can I add 1 to their names, for example, to get 0002.png and 0003.png from 0001.png and 0002.png respectively, without overwriting?




• How can I subtract 2 from their names, so that 0100.png will not become 098.png but 0098.png instead?

Related https://stackoverflow.com/questions/26770060/subtracting-a-number-from-the-names-of-all-the-files-in-a-directory, but more difficult here.

I would probably end up using temporary directory in this case:

for file in [[:digit:]]*.png; do
 echo mv $file tmp/$(printf %04d $((10#$file%.png+1))).png
done

The important part is 10#N which forces bash to interpret 000N as just N, otherwise leading zeros denotes octal numbers.

For example:

$ touch 0001.png 0002.png 0010.png 0020.png 0100.png 0200.png
$ for file in [[:digit:]]*.png; do echo mv $file tmp/$(printf %04d $((10#$file%.png-1))).png; done
mv 0001.png tmp/0000.png
mv 0002.png tmp/0001.png
mv 0010.png tmp/0009.png
mv 0020.png tmp/0019.png
mv 0100.png tmp/0099.png
mv 0200.png tmp/0199.png

The solution for (1)

Sort the files according to their numbers and start renaming with the one with the highest number. That makes collisions impossible.

ls *.png | sort -rn | while read ...; do ... mv ...; done

The solution for (2)

Determine the number of digits (if it not the same for all files) and then use printf for keeping that length:

printf %04d.png 98
0098.png

Using Perl's rename :

-2 :

$ rename -n 's@bd+b@sprintf("%04d", $& - 2)@e' 0100.png
0100.png -> 0098.png

+1 :

$ rename -n 's@bd+b@sprintf("%04d", $& + 1)@e' 0001.png 0002.png
0001.png -> 0002.png
0002.png -> 0003.png

You can remove the -n (dry-run mode switch) when your tests become valids.

There are other tools with the same name which may or may not be able to do this, so be careful.

If you run the following command (linux)

$ file $(readlink -f $(type -p rename))

and you have a result like

.../rename: Perl script, ASCII text executable

then this seems to be the right tool =)

If not, to make it the default (usually already the case) on Debian and derivative like Ubuntu :

$ sudo update-alternatives --set rename /path/to/rename

(replace /path/to/rename to the path of your perl's rename command.

If you don't have this command, search your package manager to install it or do it manually

Last but not least, this tool was originally written by Larry Wall, the Perl's dad.