Bash-it to pieces! Part two!

So I finished my Bash Scripting tutorial! YAY! I still have to run it to see if it works in my home directory but I think I got it to work! YAY! Still having troubles forcing Cygwin to change my home directory.

             #first check for the various 'modes' that this program has
             #if the first ($1) condition matches then we execute that 

             #portion of the
             #program and then exit
             
             # check for the prefix condition
             if [ $1 = p ]; then
             
             #we now get rid of the mode ($1) variable and prefix ($2)
               prefix=$2 ; shift ; shift
             
             # a quick check to see if any files were given
             # if none then its better not to do anything than rename some 

             # non-existent
             # files!!
             
               if [$1 = ]; then
                  echo "no files given"
                  exit 0
               fi
             
             # this for loop iterates through all of the files that we gave the 

             # program
             # it does one rename per file given
               for file in $*
                 do
                 mv ${file} $prefix$file
               done
             
             #we now exit the program
               exit 0
             fi
             
             # check for a suffix rename
             # the rest of this part is virtually identical to the previous section
             # please see those notes
             if [ $1 = s ]; then
               suffix=$2 ; shift ; shift
             
                if [$1 = ]; then
                 echo "no files given"
                exit 0
                fi
             
              for file in $*
               do
                mv ${file} $file$suffix
              done
             
              exit 0
             fi
             
             # check for the replacement rename
             if [ $1 = r ]; then
             
               shift
             
             # i included this bit as to not damage any files if the user does 

             # not specify
             # anything to be done
             # just a safety measure
             
               if [ $# -lt 3 ] ; then
                 echo "usage: renna r [expression] [replacement] files... "
                 exit 0
               fi
             
             # remove other information
               OLD=$1 ; NEW=$2 ; shift ; shift
             
             # this for loop iterates through all of the files that we give the program
             # it does one rename per file given using the program 'sed'
             # this is a sinple command line program that parses standard input and
             # replaces a set expression with a give string
             # here we pass it the file name ( as standard input) and replace the nessesary
             # text
             
               for file in $*
               do
                 new=`echo ${file} | sed s/${OLD}/${NEW}/g`
                 mv ${file} $new
               done
             exit 0
             fi
             
             # if we have reached here then nothing proper was passed to the program
             # so we tell the user how to use it
             echo "usage;"
             echo " renna p [prefix] files.."
             echo " renna s [suffix] files.."
             echo " renna r [expression] [replacement] files.."
             exit 0
             
             # done!