UNIX rename script, DOS Style

[abeath08]

HI,
as part of my college work, I have to create a UNIX command which can rename in the style of the DOS rename. I have the basic code working, which will rename the files. But i cant seem to get the file extension, rename bit sorted. I think it might be my regex but not sure, any help would be good. Here is the code i have so far, please ignore the error checking:

#!/bin/sh
#
# - A DOS STYLE RENAME
#
case $# in
0)            echo "Usage: dosRename file [ ... ] target"
            exit
            ;;
#2)            echo "dosRename: $file: Can't have anything after target"
#            exit
#            ;;
'..')        echo "dosRename: $file: Can't have more than one dot"
            exit
            ;;
'**')          echo "dosRename: $file: Can't have more than one asterisk"
            exit
            ;;
#[!-f])      echo "dosRename: $file: Doesn't exist"
#            exit
#            ;;
6)          echo "dosRename: $file: Must have a dot"
            exit
            ;;
7)            echo "dosRename: No target"
            exit
            ;;
*)            for file
            do
                case $file in
                [A-Za-z0-9]*\.\*)     filePart=name
                                    ;;
                \*\.[A-Za-z0-9]*)     filePart=etx
                                    ;;
                esac
            done
            endFile=$file
            fileName=`echo $endFile | sed -e 's/\.\*//'`
            extension=`echo $endFile | sed -e 's/\*\./\./'`
            while [ $# -ne 1  ]
            do
                    case $filePart in
                        'name')     result=`echo $1 | sed -e "s/[A-Za-z0-9]*\.\(.*[A-Za-z0-9]*\)/$fileName\.\1/"`
                                    mv $1 $result
                                    ;;
                        'ext')        result=`echo $1 |sed -e "s/\.[A-Za-z0-9]*/$extension/"`
                                    mv $1 $result
                                    ;;
                    esac
                 shift 1
            done
             ;;
esac

any advice would be great on where i might possibly be going wrong.
also i am unable to use python as we have not yet covered it in the course,
thanks guys

[Cabhan]

Well, first off, this is misspelled:

filePart=etx

Secondly, your code seems extremely complicated for this task, and in any event, it is against the forum rules to help with homework assignments. If you can narrow down your question to something specific, we can help you then.

[abeath08]

well thats got it sorted thanks. but its hardly doing my homework as all of the coding is already done.

[Cabhan]

Except that the coding isn't already done, as it has errors. Whereas the question "I wrote this script, and this particular line isn't working. It's supposed to do this, but instead it's doing this." is a good way to ask about homework.