Question

I have a text file with protein sequences. I would like to replace all the lowercase letters to upper case letter ‘C’. How can I do this with awk?

>1CHE
aHKLbMaHc
>2HV3
PNMRrYnf
>5GH3
LKDeVmqQ

desired output

>1CHE
CHKLCMCHC
>2HV3
PNMRCYCC
>5GH3
LKDCVCCQ

Answer 1

I would use sed for this:

sed '/^>/!s/[a-z]/C/g' file.txt

If you’d like the awk, here it is:

awk '!/^>/ { gsub(/[a-z]/, "C") }1' file.txt

Results:

>1CHE
CHKLCMCHC
>2HV3
PNMRCYCC
>5GH3
LKDCVCCQ