đģ Grep
Recursive: check subdirectories
grep -r term4search /dir
grep -v term2exclude /dir/file
egrep -w 'term1|term2' /dir/file
grep -i searchterm /dir/file
grep -e term1 -e term2 -e term3 /dir/file
.txt, .mp3, .svg, .sh, .bash, .conf, etc.
grep -e term1 -e term2 /dir/*.txt