grep is a programming language created in 1974.
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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.. Read more on Wikipedia...
$ grep root /etc/passwd root:x:0:0:root:/root:/bin/bash operator:x:11:0:operator:/root:/sbin/nologin $ grep -n root /etc/passwd 1:root:x:0:0:root:/root:/bin/bash 12:operator:x:11:0:operator:/root:/sbin/nologin $ grep -c false /etc/passwd 7