snake

#!/bin/bash

# snake: convert filenames to snake case

progname=$(basename "$0")

while [ "$#" -gt 0 ] ; do

    filename=$(basename "$1")
    directory=$(dirname "$1")

    if [ ! \( -f "$filename" \) ]; then
        echo "$progname: '$filename' doesn't exist or is not a file." 1>&2
        exit 1
    fi

    if [ ! \( -w "$filename" \) ]; then
        echo "$progname: directory '$directory' has no write permission." 1>&2
    fi

    filename_no_ext="${filename%.*}"
    ext="${filename##*.}"

    if [ "$filename_no_ext" = "$ext" ] ; then
        ext=
    else
        ext=".$ext"
    fi

    new_filename_no_ext=$(tr '()_\ ,.' '-' <<< "$filename_no_ext")
    new_filename_no_ext=$(sed 's/\([[:lower:]]\)\([[:upper:]]\)/\1-\2/g' <<< "$new_filename_no_ext")
    new_filename_no_ext=$(sed 's/^-//' <<< "$new_filename_no_ext")
    new_filename_no_ext=$(sed 's/-$//' <<< "$new_filename_no_ext")
    new_filename_no_ext=$(sed 's/'"'"'//' <<< "$new_filename_no_ext")
    new_filename_no_ext="${new_filename_no_ext,,}"
    new_filename_no_ext=$(sed 's/-\+/-/g' <<< "$new_filename_no_ext")
    new_filename_no_ext=$(iconv -f utf8 -t ascii//TRANSLIT <<< "$new_filename_no_ext")

    new_filename="${new_filename_no_ext}${ext}"

    if [ "$filename" -ef "$new_filename" ] ; then
        echo "'$filename' won't be renamed."
    else
        echo "'$filename' will be renamed to '$new_filename'."
        mv "$filename" "$new_filename"
    fi

    shift

done

echo -e "\nDone!"
exit 0