A regular expression is a pattern that describes a set of strings.
Regular expressions are constructed analogously to arithmetic expressions,
by using various operators to combine smaller expressions.
three different versions of regular expression syntax:
“basic,” (BRE) “extended” (ERE) and “perl”.
there is no difference in available functionality between the basic and
In other implementations, basic regular expressions are less powerful.
The following description applies to extended regular expressions;
differences for basic regular expressions are summarized afterwards.
Perl regular expressions give additional functionality, and are
documented in the pcresyntax(3) and pcrepattern(3) manual pages,
but work only if PCRE is available in the system.
|• Fundamental Structure:|
|• Character Classes and Bracket Expressions:|
|• The Backslash Character and Special Expressions:|
|• Back-references and Subexpressions:|
|• Basic vs Extended:|