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The pcregrep command is an implementation of grep that uses Perl regular expression syntax. [17] Similar functionality can be invoked in the GNU version of grep with the -P flag. [18] Ports of grep (within Cygwin and GnuWin32, for example) also run under Microsoft Windows. Some versions of Windows feature the similar qgrep or findstr command. [19]
For example, GNU grep has the following options: "grep -E" for ERE, and "grep -G" for BRE (the default), and "grep -P" for Perl regexes. Perl regexes have become a de facto standard, having a rich and powerful set of atomic expressions.
Utilities listed in POSIX.1-2017. This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS).
In the above example, the find utility feeds the input of xargs with a long list of file names. xargs then splits this list into sublists and calls rm once for every sublist. Some implementations of xargs can also be used to parallelize operations with the -P maxprocs argument to specify how many parallel processes should be used to execute the ...
The default is to attempt the longest match first and backtrack through shorter matches: e.g. a.*?b would match first "ab" in "ababab", where a.*b would match the entire string. If the U flag is set, then quantifiers are ungreedy (lazy) by default, while ? makes them greedy.
The classic filter in Unix is Ken Thompson's grep, which Doug McIlroy cites as what "ingrained the tools outlook irrevocably" in the operating system, with later tools imitating it. [1] grep at its simplest prints any lines containing a character string to its output. The following is an example:
ngrep (network grep) is a network packet analyzer written by Jordan Ritter.It has a command-line interface, and relies upon the pcap library and the GNU regex library.. ngrep supports Berkeley Packet Filter logic to select network sources or destinations or protocols, and also allows matching patterns or regular expressions in the data payload of packets using GNU grep syntax, showing packet ...
agrep (approximate grep) is an open-source approximate string matching program, developed by Udi Manber and Sun Wu between 1988 and 1991, [1] for use with the Unix operating system. It was later ported to OS/2 , DOS , and Windows .