grep

• grep for $string1 AND $string2:

grep -RiE 'rabbit.*guest' /etc/*

• diff files and show only common lines:

grep -F -x -f file1 file2

• find all files containing a string and run sed command against them:

files=$(git grep -l "kind: HelmRelease" | grep -v gotk) && echo $files | xargs sed -i 's/v2beta1/v2beta2/g'