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agrep (approximate grep) is an open-source approximate string matching program, developed by Udi Manber and Sun Wu between 1988 and 1991, [26] for use with the Unix operating system. It was later ported to OS/2, DOS, and Windows. agrep matches even when the text only approximately fits the search pattern. [27]
Regular expressions entered popular use from 1968 in two uses: pattern matching in a text editor [9] and lexical analysis in a compiler. [10] Among the first appearances of regular expressions in program form was when Ken Thompson built Kleene's notation into the editor QED as a means to match patterns in text files.
grep is a command-line utility for searching plain-text data sets for lines matching a regular expression and by default reporting matching lines on standard output. tree is a command-line utility that recursively lists files found in a directory tree, indenting the filenames according to their position in the file hierarchy.
It combines ideas from Aho–Corasick with the fast matching of the Boyer–Moore string-search algorithm. For a text of length n and maximum pattern length of m, its worst-case running time is O(mn), though the average case is often much better. [2] GNU grep once implemented a string matching algorithm very similar to Commentz-Walter. [3]
/L Uses search strings literally. /R Uses search strings as regular expressions. /S Searches for matching files in the current directory and all subdirectories. /I Specifies that the search is not to be case-sensitive. /X Prints lines that match exactly. /V Prints only lines that do not contain a match. /N Prints the line number before each ...
The matching algorithms of the library are based on the PCRE library, but not all of the PCRE library is interfaced and some parts of the library go beyond what PCRE offers. Currently PCRE version 8.40 (release date 2017-01-11) is used. Erlang: erlang.org: Apache 2.0: Standard library includes PCRE-based re module. The matching algorithms of ...
A separate special buffer, the hold space, may be used by a few sed commands to hold and accumulate text between cycles. sed's command language has only two variables (the "hold space" and the "pattern space") and GOTO-like branching functionality; nevertheless, the language is Turing-complete, [6] [7] and esoteric sed scripts exist for games ...
TRE is an open-source library for pattern matching in text, [2] which works like a regular expression engine with the ability to do approximate string matching. [3] It was developed by Ville Laurikari [1] and is distributed under a 2-clause BSD-like license.