Ed (text editor)

ed

Original author(s)	Ken Thompson
Initial release	1971, 45–46 years ago
Operating system	Unix-like
Type	Text editor

ed is a line editor for the Unix operating system. It was one of the first parts of the Unix operating system that were developed, in August 1969. It remains part of the POSIX and Open Group standards for Unix-based operating systems, alongside more sophisticated full-screen editors such as vi.

The ed text editor was one of the first three key elements of the Unix operating system—assembler, editor, and shell—developed by Ken Thompson in August 1969 on a PDP-7 at AT&T Bell Labs. Many features of ed came from the qed text editor developed at Thompson's alma mater University of California at Berkeley. Thompson was very familiar with qed, and had reimplemented it on the CTSS and Multics systems. Thompson's versions of qed were notable as the first to implement regular expressions. Regular expressions are also implemented in ed, though their implementation is considerably less general than that in qed.

Dennis M. Ritchie produced what Doug McIlroy later described as the "definitive" ed, and aspects of ed went on to influence ex, which in turn spawned vi. The non-interactive Unix command grep was inspired by a common special uses of qed and later ed, where the command g/re/p means globally search for the regular expression re and print the lines containing it. The Unix stream editor, sed implemented many of the scripting features of qed that were not supported by ed on Unix. In turn sed influenced the design of the programming language AWK – which inspired aspects of Perl.

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