Question

This could easily be any lang…but I’m using bash for now. I’m looking for the understanding behind this that can be replicated across langs.

so…

I’m copying a file up the directory tree and than replacing that file with another.

     cp "$DIR"/folder2/file2 "$DIR";
     mv "$DIR"/folder1/file1 "$DIR"/folder2/file2;

Then I take the copied file and move it into another folder..starting the same dance.

     cp "$DIR"/folder3/file3 "$DIR";
     mv "$DIR"/file2 "$DIR"/folder3/file3

I want to do this like 100 times+.

what’s the most elegant way?

Elegant, in the sense of brief and understandable by someone else.

Answer 1

You’re trying to:

1. Backup file B.
2. Rename (or move) file A as file B.
3. Backup file C.
4. Rename backup of file B as file C.
5. Backup file D.
6. Rename backup of file C as file D.

and so on.

It’s actually easier to do it backwards such that you only need to backup the last file.

last=100
mv "$DIR/folder$last/file$last" "$DIR"
for i in $(seq $last -1 2); do
  mv "$DIR/folder$((i-1))/file$((i-1))" "$DIR/folder$i/file$i"
done 

Note:

• seq $last -1 2 generates a sequence of numbers from $last up to 2 by increments of -1.
• I’m using seq instead of brace expansion because the latter doesn’t expand numbers when you have {$last .. 1}