(Global Regular Expression and Print) A Unix pattern matching utility that searches files for a string of text and outputs the line that contains the pattern. Grep came from ed, a Unix text editor, in which the command g/re/p meant "display all text in the file that matches this." That single function became a utility itself, available on all major platforms today. This is an example of the rich family of command line functions built into Unix long before WindowsThe following real life example used grep to find occurrences of the text "xfiles.lst" within any .CMD files in the default folder. The results show the matching files and text. See Unix.
To use a program such as grep to search in a file.
By extension, to search anything (perhaps a paper document by eye).