SCRIPTS for TOUCH

Question

I've seen a useful command like this:

for f in *; do t=$(echo $f | sed -E 's/[-. mov]//g'); touch -t $t "$f"; done

What do I need to change in that command, in order to keep only the "time stamp" string for a file with the following naming convention?

aaaa@XXXXXX(XXXXXXX)_20170201101315.mp3

Answer 1

I'd take a little different approach, in that I'd want to test that the filename ends in .mp3 and the length of the t variable is 12 characters long before processing. This should keel it from acting on files that do not conform to the pattern and avoid throwing errors, even though the errors in this case should be non-fatal. I just don't like unnecessary junk outputted.

This is an example of it in script form:

#!/bin/bash

for f in *.mp3; do
    t="$(awk '/_.*/ { match($0, /_.*/); print substr($0, RSTART + 1, RLENGTH - 7); }'<<<"$f")"
        if [[ ${#t} -eq 12 ]]; then
            touch -t "$t" "$f"
        fi
done

This is an example of the script as a one-liner, albeit a long one.

for f in *.mp3; do t="$(awk '/_.*/ { match($0, /_.*/); print substr($0, RSTART + 1, RLENGTH - 7); }'<<<"$f")"; if [[ ${#t} -eq 12 ]]; then touch -t "$t" "$f"; fi; done

Which can be shortened to:

for f in *.mp3; do t="$(awk '/_.*/ { match($0, /_.*/); print substr($0, RSTART + 1, RLENGTH - 7); }'<<<"$f")"; [[ ${#t} -eq 12 ]] && touch -t "$t" "$f"; done

If you really want to shorten it further:

for f in *; do t="$(awk '/_.*/ { match($0, /_.*/); print substr($0, RSTART + 1, RLENGTH - 7); }'<<<"$f")"; touch -t "$t" "$f" 2>/dev/null; done

The above form of the compound command does no error checking and redirects the error output of the touch command so it doesn't clutter the screen. This form is fine in this use case as a malformed touch commands will be non-fatal.

Answer 2

You can practice on the command line to get a working sed script:

$ echo "aaaa@XXXXXX(XXXXXXX)_20170201101315.mp3" | sed -e "s/^.*_//g" -e "s/\.mp3$//g"
20170201101315

Since the timestamp in your filename includes the seconds and it's not in a format that touch accepts (it wants a '.' before the seconds), I exclude them with a cut:

for f in *; do t=$(echo $f |  sed -e "s/^.*_//g" -e "s/\.mp3$//g" | cut -c -12); echo touch -t $t "$f"; touch -t $t "$f"; done