Shell script to rename files based on suffix

Given below is a Shell script to rename files based on suffix.

Links that you may find important :

http://linux.about.com/od/commands/l/blcmdl1_ls.htm
http://en.wikipedia.org/wiki/Ls
http://linux.about.com/library/cmd/blcmdl1_wc.htm
http://www.computerhope.com/unix/uwc.htm
http://en.wikipedia.org/wiki/Wc_%28Unix%29
http://en.wikipedia.org/wiki/Cut_%28Unix%29
http://linux.about.com/od/commands/l/blcmdl1_cut.htm
http://linux.about.com/library/cmd/blcmdln_expr.htm
http://en.wikipedia.org/wiki/Expr

Code :

#!/bin/sh 
if [ $# -ne 2 ]
then
    echo "Please enter 2 arguments"
    exit
fi

echo "files with suffix $1"
ls *$1
suffix_len=`echo $1|wc -c`
echo "suffix length = $suffix_len"
filelist=`ls *$1`
echo $filelist
num_of_files=`echo $filelist| wc -w`
echo $num_of_files

c=1
while [ $c -le $num_of_files ]
do
    file_name=`echo $filelist| cut -d" " -f$c`
    echo "File Name = $file_name"
    file_len=`echo $file_name| wc -c`
    echo "Filename Length = $file_len"
    n=`expr $file_len - $suffix_len`
    echo "n = $n"
    file_prefix=`echo $file_name| cut -c1-$n`
    echo "Prefix of File = $file_prefix"
    mv $file_name $file_prefix$2
    c=`expr $c + 1`
done
filelist=`ls *$1`
echo $filelist

Output :

files with suffix txt
a.txt btxt ctxt
suffix length = 4
a.txt btxt txt
3
File Name = a.txt
Filename Length = 6
n = 2
Prefix of File = a.
File Name = btxt
Filename Length = 5
n = 1
Prefix of File = b
File Name = ctxt
Filename Length = 5
n = 1
Prefix of File=c
a.text btext ctext

Note : Leave a comment if you feel the program is incorrect and/or has errors and/or if the program and its output don't match. Please report about broken links.