FreeGrep

The grep utility searches any given input files, selecting lines that match one or more patterns. By default, a pattern matches an input line if the regular expression in the pattern matches the input line without its trailing newline. An empty expression matches every line. Each input line that matches at least one of the patterns is written to the standard output. grep is used for simple patterns and basic regular expressions; egrep can handle extended regular expressions. fgrep is quicker than both grep and egrep, but can only handle fixed patterns (i.e. it does not interpret regular expressions). Patterns may consist of one or more lines, allowing any of the pattern lines to match a portion of the input. zgrep, zegrep, and zfgrep act like grep, egrep, and fgrep, respectively, but accept input files compressed with the compress or gzip compression utilities.