Diff Command – Compare Directories Ignoring Extensions

To see a listing, here are two variants, one that recurses into subdirectories and one that doesn't. All use syntax specific to bash, ksh and zsh.

comm -3 <(cd source && find -type f | sed 's/\.[^.]*$//' | sort) \
        <(cd dest && find -type f | sed 's/\.[^.]*$//' | sort)
comm -3 <(cd source && for x in *; do printf '%s\n' "${x%.*}"; done | sort) \
        <(cd dest && for x in *; do printf '%s\n' "${x%.*}"; done | sort)

Shorter, in zsh:

comm -3 <(cd source && print -lr **/*(:r)) <(cd dest && print -lr **/*(:r))
comm -3 <(print -lr source/*(:t:r)) <(print -lr dest/*(:t:r))

The comm command lists the lines that are common to two files (comm -12), that are only in the first file (comm -23) or that are only in the second file (comm -13). The numbers indicate what is subtracted from the output¹. The two input files must be sorted.

Here, the files are in fact the output of a command. The shell evaluates the <(…) construct by providing a “fake” file (a FIFO or a /dev/fd/ named file descriptor) as the argument to the command.

¹ _{So here the minus sayers are fully justified.}

If you want to perform actions on the files, you'll probably want to iterate over the source files.

cd source
for x in *; do
  set -- "…/dest/${x%.*}".*
  if [ $# -eq 1 ] && ! [ -e "$1" ]; then
    echo "$x has not been converted"
  elif [ $# -gt 1 ]; then
    echo "$x has been converted to more than one output file: " "$@"
  else
    echo "$x has been converted to $1"
  fi
done

for dir in */*; do           # loop over the directories
    (                        # run in a subshell ...
        cd "$dir"            # ... so we don't have to cd back
        files=(*)            # store the filenames in a zero-indexed array

        for index in "${!files[@]}"; do
            file=${files[$index]}
            ext=${file##*.}
            newname=$(printf "%02d.%s" $((index+1)) "$ext")
            mv "$file" "$newname"
        done
    )
done

Suppose you have a file with no extension. In that case it will have the same name except with leading numbers (e.g. my_file => 05.my_file)

All non-hidden directory entries will be renamed, including directories.