Features
Features of ed include:
- available on essentially all Unix systems (and mandatory on systems conforming to the Single Unix Specification).
- a modal editor supporting command mode, text mode and viewing mode
- support for regular expressions
- powerful automation can be achieved by feeding commands from standard input
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.
Read more about this topic: Ed (text Editor)
Famous quotes containing the word features:
“All visible objects, man, are but as pasteboard masks. But in each event—in the living act, the undoubted deed—there, some unknown but still reasoning thing puts forth the mouldings of its features from behind the unreasoning mask. If man will strike, strike through the mask!”
—Herman Melville (1819–1891)
“Each reader discovers for himself that, with respect to the simpler features of nature, succeeding poets have done little else than copy his similes.”
—Henry David Thoreau (1817–1862)
“These, then, will be some of the features of democracy ... it will be, in all likelihood, an agreeable, lawless, particolored commonwealth, dealing with all alike on a footing of equality, whether they be really equal or not.”
—Plato (c. 427–347 B.C.)