Ed (text editor)

ed is the standard text editor on the Unix operating system. ed was originally written by Ken Thompson and contains one of the first implementations of regular expressions. Prior to that implementation, the concept of regular expressions was only formalized in a mathematical paper, which Ken Thompson had read. ed was influenced by an earlier editor known as QED from University of California at Berkeley, Ken Thompson's alma mater. ed went on to influence ex, which in turn spawned vi. The non-interactive Unix commands grep and sed were inspired by common special uses of ed; their influence is visible in the design of the programming language AWK, which in turn inspired aspects of Perl.

Famous for its terseness, ed gives almost no visual feedback. For example, the message that ed will produce in case of error, or when it wants to make sure the user wishes to quit without saving, is "?". It does not report the current filename or line number, or even display the results of a change to the text, unless requested. This terseness was appropriate in the early versions of Unix, when consoles were teletypes, modems were slow, and memory was precious. As computer technology improved and these constraints were loosened, editors with more visual feedback became the standard.

In current practice, ed is rarely used interactively, but does find use in some shell scripts. For interactive use, ed was subsumed by the sam, vi and Emacs editors in the 1980s. ed can be found on virtually every version of Unix and Linux available, and as such is useful for people who have to work with multiple versions of Unix. If something goes wrong, ed is sometimes the only editor available. This is often the only time when it is used interactively.

The ed commands are often imitated in other line-based editors. For example, EDLIN in early MS-DOS versions and 32-bit versions of Windows NT has a somewhat similar syntax, and text editors in many MUDs (LPMud and descendants, for example) use ed-like syntax. These editors, however, are typically more limited in function.


Here is an example transcript of an ed session. For clarity, commands and text typed by the user are in normal face, and output from ed is emphasized.

a ed is the standard Unix text editor. This is line number two. . 2i . %l ed is the standard Unix text editor.$ $ This is line number two.$ 3s/two/three/ ,l ed is the standard Unix text editor.$ $ This is line number three.$ w text 65 q

The end result is a simple text file containing the following text:

ed is the standard Unix text editor. This is line number three.

Started with an empty file, the "a" command appends text (all ed commands are single letters). The command put ed in "insert mode", inserting the characters that follow and is terminated by a single dot on a line. The two lines that are entered before the dot end up in the file buffer. The "2i" command also goes into insert mode, and will insert the entered text (a single empty line in our case) before line two. All commands may be prefixed by a line number to operate on that line.

In "%l" the l stands for the list command. The command is prefixed by a range, in this case "%" which is a shortcut for "1,$". A range is two line numbers separated by a comma ("$" means the last line). In return, ed lists all lines, from first to last. These lines are ended with dollar signs, so that white space at the end of lines is clearly visible.

The error in line 3 is corrected with "3s/two/three/", a substitution command. The "3" will apply it to the correct line, following the command is the text to be replaced, and then the replacement. Listing all lines with ",l" (a lone comma is also a synonym for "%") the line is shown now to be correct.

"w text" writes the buffer to the file "text" making ed respond with "65", the number of characters written to the file. "q" will end an ed session.

Bill Joy, vi, and ed

In the editor wars, Emacs proponents used to say, "even Bill Joy doesn't use vi anymore."

In a 1984 interview [http://web.cecs.pdx.edu/~kirkenda/joy84.html Interview with Bill Joy, Unix Review, August 1984.] Bill Joy explained that, at Sun, he used an early desktop publishing program, called Interleaf; when visiting labs outside Sun, he used plain old ed. Although vi was almost ubiquitous, he could not count on the local version working the way he expected. However, ed was never modified, so he could count on making it work without making himself look like a fool.

See also

*Edlin, the standard MS-DOS line editor.
*List of Unix programs
*Editor wars


External links

* [http://www.gnu.org/software/ed/ed.html GNU ed homepage]
* [http://gnuwin32.sourceforge.net/packages/ed.htm GNU ed for Win32]
* [http://snap.nlc.dcccd.edu/learn/nlc/ed.html Unix Editors I]
* [http://bash-hackers.org/wiki/doku.php?id=howto:edit-ed Examples for ed in scripts]
* [http://www.gnu.org/fun/jokes/ed.msg.html ed Humor]

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Text Editor and Corrector — TECO (pronounced /tee koh/; originally an acronym for [paper] Tape Editor and COrrector , but later Text Editor and COrrector ) is a text editor originally developed at the Massachusetts Institute of Technology (MIT) in the 1960s, after which it… …   Wikipedia

  • text editor — text′ ed itor n. cmp a computer program for writing and modifying documents or program code on screen, usu. having little or no formatting ability • Etymology: 1970–75 text′ ed it•ing, adj …   From formal English to slang

  • Text-Editor — Texteditor Ein Texteditor (lat. editor „Herausgeber“, „Erzeuger“) ist ein Computerprogramm zum Bearbeiten von Texten. Der Editor lädt die zu bearbeitende Textdatei und zeigt ihren Inhalt auf dem Bildschirm an. Durch diverse Aktionen können die… …   Deutsch Wikipedia

  • Univac Text Editor — @ED or ED 1100 is the original interactive text editor implemented on the UNIVAC 1100/2200 series. The editor was originally developed by Dr. Roger M. Firestone in the mid 1970s.TrademarkUNIVAC has been, over the years, a registered trademark of …   Wikipedia

  • Sam (text editor) — Infobox Software name = Sam caption = collapsible = author = Rob Pike developer = Bell Labs released = early 1980 s latest release version = latest release date = July 4, 2003 latest preview version = latest preview date = frequently updated =… …   Wikipedia

  • mined (text editor) — MinEd Mined editing Unicode text Developer(s) Thomas Wolff Stable release 2011.17 / June 2011 …   Wikipedia

  • Mined (text editor) — Infobox Software name = Mined caption = Mined editing Unicode text developer = [http://towo.net/mined Thomas Wolff] latest release version = 2000.14 latest release date = July 2007 operating system = OS independent genre = Text editor license =… …   Wikipedia

  • Ex (text editor) — ex, short for EXtended, is a line editor for Unix systems.The original ex was an advanced version of the standard Unix editor ed, included in the Berkeley Software Distribution. ex is similar to ed, with the exception that some switches and… …   Wikipedia

  • QED (text editor) — QED is a line oriented computer text editor that was designed by Butler Lampson and L. Peter Deutsch for the Berkeley Timesharing System running on the SDS 940. It was implemented by L. Peter Deutsch and Dana Angluin between 1965 and 1966. [cite… …   Wikipedia

  • Se (text editor) — se (screen editor) is also known as the Georgia Tech Screen Editor .According to the README file in its sources, Se started out as the version of ed that came with the book Software Tools , by Kernighan and Plauger, which was written in… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”