grep

grep aaabbbccc /home/usr/data/*
grep aaabbbccc *
grep -i pattern file ---- dont match case
grep -l pattern file ---- only show the file names
grep -w pattern file ---- match whole word
grep -C 5 pattern file ---- show 5 more line around
grep pattern1 file | grep pattern2 ---- pattern1 & pattern2

grep -d skip ---- skip sub-directory
grep -r ---- search directory