Sed

sed ("stream editor") is a Unix utility that parses and transforms text, using a simple, compact programming language. It was developed from 1973 to 1974 by Lee E. McMahon of Bell Labs, and is available today for most operating systems. sed was based on the scripting features of the interactive editor ed ("editor", 1971) and the earlier qed ("quick editor", 1965–66). It was one of the earliest tools to support regular expressions, and remains in use for text processing, most notably with the substitution command. Popular alternative tools for plaintext string manipulation and "stream editing" include AWK and Perl.

Usage
Always use the -n option to suppress printing all the lines which is a really dumb thing

sed -i 's/{OLD_TERM}/{NEW_TERM}/' {file}

replaces within file not stream

Tutorials

 * Sed - An Introduction and Tutorial, by Bruce Barnett
 * SED -- A Non-interactive Text Editor (1974), by Lee E. McMahon
 * 31+ Examples For Sed Linux Command In Text Manipulation, by Mokhtar Ebrahim

Examples

 * Major sources for sed scripts, files, usage
 * Roger Chang's SED and Shell Scripts (2012)
 * Top 'sed' commands – Usage examples
 * Sed command examples in Unix & Linux

Other links

 * (includes manual)