Sed
| Paradigm | scripting |
|---|---|
| Designed by | Lee E. McMahon |
| First appeared | 1974 |
| Implementation language | C |
| Influenced by | |
| ed | |
| Influenced | |
| Chomski, Perl, AWK | |
sed (stream editor) is a Unix utility that parses and transforms text, using a simple, compact programming language. sed 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). sed was one of the earliest tools to support regular expressions, and remains in use for text processing, most notably with the substitution command. Other options for doing "stream editing" include AWK and Perl.
First appearing in Version 7 Unix, sed is one of the early Unix commands built for command line processing of data files. It evolved as the natural successor to the popular grep command. The original motivation was an analogue of grep (g/re/p) for substitution, hence "g/re/s". Foreseeing that further special-purpose programs for each command would also arise, such as g/re/d, McMahon wrote a general-purpose line-oriented stream editor, which became sed. The syntax for sed, notably the use of / for pattern matching, and s/// for substitution, originated with ed, the precursor to sed, which was in common use at the time, and the regular expression syntax has influenced other languages, notably ECMAScript and Perl. Later, the more powerful language AWK developed, and these functioned as cousins, allowing powerful text processing to be done by shell scripts. sed and AWK are often cited as progenitors and inspiration for Perl, and influenced Perl's syntax and semantics, notably in the matching and substitution operators.
GNU sed added several new features, including in-place editing of files. Super-sed is an extended version of sed that includes regular expressions compatible with Perl. Another variant of sed is minised, originally reverse-engineered from 4.1BSD sed by Eric S. Raymond and currently maintained by René Rebe. minised was used by the GNU Project until the GNU Project wrote a new version of sed based on the new GNU regular expression library. The current minised contains some extensions to BSD sed but is not as feature-rich as GNU sed. Its advantage is that it is very fast and uses little memory. It is used on embedded systems and is the version of sed provided with Minix.
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