How to batch rename files using bash

I know there are lots of such questions, but I couldn't find one (or a combination of several), which describes the things I want to do. I think I need to use regular expressions, but I am not very good with that. I use zsh. I have a folder with files, which I want to rename:

• I want the files challenge1.rb, challenge2.rb, challenge3.rb, etc. to be renamed to c1.rb, c2.rb etc. Similarly task1.rb and similar must be renamed to t1.rb etc.




• sample_spec_c1.rb, sample_spec_c2.rb etc. must be renamed to c1_spec.rb, c2_spec.rb etc.

So I guess I need some combination of regular expressions and iteration, but I don't know how to write the bash script.

Answer

Here is a short script which will do what you want. You can call the script with a list of files like: ./scriptname *.rb or with directories (it will recurse them): ./scriptname .

Do not forget to set the executable bit: chmod a+x scriptname.

#!/bin/sh

suff=rb     # suffix of files to rename


script="$0" # this script name for recursion

for f in "$@" ; do
    if test -d "$f" ; then
        echo "=== recursing directory $f"
        find "$f" -type f -name "*.$suff" -exec "$script" {} +
    elif test -f "$f" ; then
        d="$(dirname "$f")"
        b="$(basename "$f")"

        r="$(echo "$b" | sed -r "s/^([a-zA-Z])[a-zA-Z]*([0-9]+\.${suff})\$/\1\2/;s/^[a-zA-Z]+_([a-zA-Z]+)_([a-zA-Z]+[0-9]+)(\.${suff})\$/\2_\1\3/")"
        echo "-- renaming $f -> $d/$r"
        mv "$f" "$d/$r"
    fi
done