<Tr> <Th> License </Th> <Td> GNU General Public License </Td> </Tr> <Tr> <Th> Website </Th> <Td> www.gnu.org/software/grep/ </Td> </Tr> <P> grep is a command - line utility for searching plain - text data sets for lines that match a regular expression . Its name comes from the ed command g / re / p (globally search a regular expression and print), which has the same effect: doing a global search with the regular expression and printing all matching lines . Grep was originally developed for the Unix operating system, but later available for all Unix - like systems . </P> <P> The first version of grep was written overnight by Ken Thompson to help Lee E. McMahon analyze the text of the Federalist Papers to determine authorship of the individual papers . The ed text editor (also authored by Thompson) had regular expression support but could not be used on such a large amount of text, so Thompson excerpted that code into a standalone tool . Thompson chose the name because in ed, the command g / re / p would print all lines matching a previously defined pattern . grep was first included in Version 4 Unix . Stating that it is "generally cited as the prototypical software tool", Doug McIlroy credited grep with "irrevocably ingraining" Thompson's tools philosophy in Unix . </P>

There is a specific term from computer science for the patterns that grep