source: vendor/bash/3.1-p17/examples/scripts.v2/lowercase

#! /bin/bash
#
# original from
# @(#) lowercase.ksh 1.0 92/10/08
# 92/10/08 john h. dubois iii (john@armory.com)
#
# conversion to bash v2 syntax done by Chet Ramey

Usage="Usage: $name file ..."
phelp()
{
echo "$name: change filenames to lower case.
$Usage
Each file is moved to a name with the same directory component, if any,
and with a filename component that is the same as the original but with
any upper case letters changed to lower case."
}

name=${0##*/}

while getopts "h" opt; do
        case "$opt" in
        h)      phelp; exit 0;;
        *)      echo "$Usage" 1>&2; exit 2;;
        esac
done

shift $((OPTIND - 1))

for file; do
    filename=${file##*/}
    case "$file" in
    */*)    dirname=${file%/*} ;;
    *)    dirname=. ;;
    esac
    nf=$(echo $filename | tr A-Z a-z)
    newname="${dirname}/${nf}"
    if [ "$nf" != "$filename" ]; then
        mv "$file" "$newname"
        echo "$0: $file -> $newname"
    else
        echo "$0: $file not changed."
    fi
done