#!/bin/sh
# mklowercase - change all filenames to lowercase recursively from "." down.
# Will prompt if there's an existing file of that name (mv -i)

# Presumes that filenames don't include newline or tab.
# It _CAN_ handle files with spaces, initial dash, and so on, because
# "find" prefixes everything with the current directory ("." in this case).
#
# It could be modified to handle newline/tab by changing the loop to
#   find . -depth -print0 |
#   while IFS="" read -r -d '' file ; do ...
# but this requires non-standard GNU extensions to find and bash,
# as well as being far uglier/more complicated.  Also, if "mv" is implemented
# as required by the Single Unix Standard, then the "mv -i" will
# fail badly if it tries to rename a file into an existing name.
# That's because when it tries to get an answer, it will send a prompt to
# stderr, but it will expect a RESPONSE from stdin... and yet, stdin
# is where it gets the list of filenames!!
# What you REALLY need to do is forbid newline/tab from occurring in filenames.
# See: http://www.dwheeler.com/essays/fixing-unix-linux-filenames.html

# This complies with Single Unix Specification version 3.
# Really really old System V systems will need "tr" changed slightly.

set -eu
IFS=`printf '\n\t'`

for file in `find . -depth` ; do
  [ "." = "$file" ] && continue                  # Skip "." entry.
  dir=`dirname "$file"`
  base=`basename "$file"`
  oldname="$dir/$base"
  newbase=`printf "%s" "$base" | tr A-Z a-z`
  newname="$dir/$newbase"
  if [ "$oldname" != "$newname" ] ; then
    mv -i "$file" "$newname"
  fi
done