~$ whatis <command-name>
find (1) - search for files in a directory hierarchy
awk (1) - pattern scanning and processing language
grep (1) - print lines matching a pattern
sed (1) - stream editor for filtering and transforming text
cat (1) - caoncatenate files and print on the standard output
ack (1p) - grep-like text finder
ag (1) - The Silver Searcher. Like ack, but faster.