File: sed.info,  Node: Rename files to lower case,  Next: Print bash environment,  Prev: Increment a number,  Up: Examples

7.4 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 anything
     /^.*\/\(.*\)\n\1/b

     # escape special characters for the shell
     s/["$`\\]/\\&/g

     # now, transform path/fromfile\n, into
     # mv path/fromfile path/tofile and print it
     s/^\(.*\/\)\(.*\)\n\(.*\)$/mv "\1\2" "\1\3"/p

     ' | $apply_cmd