Bash script to prepend a random number to all files

Question

I have a "smart" phone that doesn't seem to have a music shuffle function, so the next best thing is to write a bash script to prepend all filenames in the current directory with a random number.

Is this difficult to do?

Answer 1

No, this is not hard to do. It will however mess up your carefully crafted filenames, and might be hard to undo.

You can use $RANDOM as a simple source of random numbers in bash. For your case:

#!/bin/bash
for file in *; do
  mv "$file" $RANDOM-"$file"
done

I didn't test this. You probably want to test this yourself on some small sample to make sure you know what it does.

Answer 2

This script will shuffle files and reshuffle them if they've already been shuffled. If you pass it an argument of -u it will unshuffle the files (remove the random prefix).

#!/bin/bash
for file in *.mp3
do
    if [[ -d $file ]]
    then
        continue    # skip directories
    fi
    if [[ $file =~ ^1[0-9]{5}9-(.*).mp3$ ]]    # get basename
    then
        name=${BASH_REMATCH[1]}                # of a previously shuffled file
    else
        name=${file%.mp3}                      # of an unshuffled file
    fi
    if [[ $1 != -u ]]
    then
        mv "$file" "1$(printf "%05d" $RANDOM)9-$name.mp3"    # shuffle
    else
        if [[ ! -e "$file.mp3" ]]
        then
            mv "$file" "$name.mp3"                           # unshuffle
        fi
    fi
done

It uses a fixed-width five digit random number after a "1" and followed by "9-" so the shuffled filenames are of the form: 1ddddd9-filename maybe with spaces - and other stuff.1983.mp3.

If you re-run the script, it will reshuffle the files by changing the random number in the prefix.

The -u argument will remove the 1ddddd9- prefix.

The script requires Bash >= version 3.2.