Rename multiple files based on pattern in Unix

Question

There are multiple files in a directory that begin with prefix fgh, for example:

fghfilea
fghfileb
fghfilec

I want to rename a

Answer 1

#!/bin/sh

#replace all files ended witn .f77 to .f90 in a directory

for filename in *.f77
do 
    #echo $filename
    #b= echo $filename | cut -d. -f1
    #echo $b    
    mv "${filename}" "${filename%.f77}.f90"    
done