![]() The fundamental building blocks are the regular expressions that match a single character. Perl regular expressions give additional functionality, and are documented in pcresyntax(3) and pcrepattern(3), but may not be available on every system. The following description applies to extended regular expressions differences for basic regular expressions are summarized afterwards. In other implementations, basic regular expressions are less powerful. Grep understands three different versions of regular expression syntax: “basic,” “extended” and “perl.” In GNU grep, there is no difference in available functionality between basic and extended syntaxes. ![]() Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. PID hash table entries: 4096 (order: 3, 32768 bytes)Ī regular expression is a pattern that describes a set of strings. SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc Rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD quiet $ grep -color -A 2 -B 2 "command line" /var/log/dmesgīuilt 1 zonelists in Zone order, mobility grouping on. The -o or -only-matching option, this has no effect and a warning is given. Places a line containing a group separator (-) between contiguous groups of matches. Places a line containing a group separator (-) between contiguous Print NUM lines of leading context before matching lines. With the -o or -only-matching option, this has no effect and a warning is given. ![]() Print NUM lines of trailing context after matching lines. ![]()
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