How to rename some file of same pattern in shell scripting

Question

I want to write a code is shell scripting which will rename all the files of extension .txt in a current directory to extension .c .Suppose my current directory contains some 10

Answer 1

awk can do this trick too:

kent$  ls *.txt|awk '{o=$0;gsub(/txt$/,"c"); print "mv "o" "$0;}'|sh