How can I replace the last character of a string with another character in bash?

Question

I am working on a small code in bash, but I am stuck on a small problem. I have a string, and I want to replace the last letter of that string with s.

For example: I am taking all the files that end in c and replacing the last c with s.

for file in *.c; do
   # replace c with s  
   echo $file

Can someone please help me?

Answer 1

for file in *.c; do 
   echo "${file%?}s"
done

In parameter substitution, ${VAR%PAT} will remove the last characters matching PAT from variable VAR. Shell patterns * and ? can be used as wildcards.

The above drops the final character, and appends "s".

Answer 2

Use parameter substitution. The following accomplishes suffix replacement. It replaces one instance of c anchored to the right with s.

for file in *.c; do
   echo "${file/%c/s}"  
done