grep-like text finder
Ack is designed as a replacement for 99% of the uses of grep. Ack searches the named input FILEs (or standard input if no files are named, or the file name - is given) for lines containing a match to the given PATTERN. By default, ack prints the matching lines. Ack can also list files that would be searched, without actually searching them, to let you take advantage of ack's file-type filtering capabilities.