(sed.info.gz) Rename files to lower case

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 Rename Files to Lower Case
 ==========================
 
    This is a pretty strange use of `sed'.  We transform text, and
 transform it to be shell commands, then just feed them to shell.  Don't
 worry, even worse hacks are done when using `sed'; I have seen a script
 converting the output of `date' into a `bc' program!
 
    The main body of this is the `sed' script, which remaps the name
 from lower to upper (or vice-versa) and even checks out if the remapped
 name is the same as the original name.  Note how the script is
 parameterized using shell variables and proper quoting.
 
      #! /bin/sh
      # rename files to lower/upper case...
      #
      # usage:
      #    move-to-lower *
      #    move-to-upper *
      # or
      #    move-to-lower -R .
      #    move-to-upper -R .
      #
      
      help()
      {
      	cat << eof
      Usage: $0 [-n] [-r] [-h] files...
      
      -n      do nothing, only see what would be done
      -R      recursive (use find)
      -h      this message
      files   files to remap to lower case
      
      Examples:
             $0 -n *        (see if everything is ok, then...)
             $0 *
      
             $0 -R .
      
      eof
      }
      
      apply_cmd='sh'
      finder='echo "$@" | tr " " "\n"'
      files_only=
      
      while :
      do
          case "$1" in
              -n) apply_cmd='cat' ;;
              -R) finder='find "$@" -type f';;
              -h) help ; exit 1 ;;
              *) break ;;
          esac
          shift
      done
      
      if [ -z "$1" ]; then
              echo Usage: $0 [-h] [-n] [-r] files...
              exit 1
      fi
      
      LOWER='abcdefghijklmnopqrstuvwxyz'
      UPPER='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
      
      case `basename $0` in
              *upper*) TO=$UPPER; FROM=$LOWER ;;
              *)       FROM=$UPPER; TO=$LOWER ;;
      esac
      
      eval $finder | sed -n '
      
      # remove all trailing slashes
      s/\/*$//
      
      # add ./ if there is no path, only a filename
      /\//! s/^/.\//
      
      # save path+filename
      h
      
      # remove path
      s/.*\///
      
      # do conversion only on filename
      y/'$FROM'/'$TO'/
      
      # now line contains original path+file, while
      # hold space contains the new filename
      x
      
      # add converted file name to line, which now contains
      # path/file-name\nconverted-file-name
      G
      
      # check if converted file name is equal to original file name,
      # if it is, do not print nothing
      /^.*\/\(.*\)\n\1/b
      
      # now, transform path/fromfile\n, into
      # mv path/fromfile path/tofile and print it
      s/^\(.*\/\)\(.*\)\n\(.*\)$/mv "\1\2" "\1\3"/p
      
      ' | $apply_cmd
 

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