copy on write, less redundant data

Question

I have a folder containing a lot of pictures and a program to update some of the pictures.

I want to make a new folder with copy of the old picture and run the program on them but I want to save space on my hdd so I don't want to have a copy of all the unchanged pictures.

Any ideas?

I am running Debian.

Answer 1

Does the program simply write over the modified picture, or create a new file and remove the old? If the latter, you can make your working directory with cp -dRl origdir workdir, which will create hard links instead of new copies. (Or cp -dRs if you'd prefer to use symbolic instead of hard links.)

Answer 2

I'd make use of /tmp and make a shell script to copy each picture there then process it. If the picture is successfully processed, move it elsewhere, if not, delete it. Do this one picture at a time.

e.g.

#!/bin/bash

for f in *
do
     cp "$f" /tmp
     /path/to/yourprogram "/tmp/$f"
     # check if picture was processed correctly, possibly via exit code ($?)
     if [ $? -eq 0 ]
     then
           mv "/tmp/$f" /some/other/location
     else
           rm "/tmp/$f"
     fi
done

Many ways to skin a cat, modify according to your needs.