bash - LINUX - grep & comment out lines from fstab -

bash - LINUX - grep & comment out lines from fstab -

i'm updating fstab on over 500 servers. current fstab has old new nfs share lines. need comment old lines. instance:

nfs.old - temp file linea lineb linec /etc/fstab - current line1 line2 linea lineb linec line3 line4

run loop input nfs.old, find line in /etc/fstab & comment it

/etc/fstab - expected fstab line1 line2 #linea #lineb #linec line3 line4

thanks!

using awk can do:

awk 'fnr==nr {a[$0];next} ($0 in a){$0="#" $0} 1' nfs.old fstab line1 line2 #linea #lineb #linec line3 line4

bash shell awk sed grep