POSIX extended regular expressions (PERE) is a way to describe string using wildcards and pattern. The following description doesn’t provide a full description of PERE but just intend to help you at the beginning.
the following rules are available:
|a|b||search for a or b|
|ab||search for the symbol a followed by symbol b|
|.||this symbol match any other.|
|a*||symbol a from 0 upto unlimited times.|
|[abc]||search for a or b or c|
|[a-z]||search for symbol between a (included) and z (included).|
|[^a-z]||search for symbol not between a (included) and z (included).|
|^abc||search for line beginning by the word abc.|
|abc$||search for line ending by the word abc.|
You can mix these rules as you need.
Here is some samples:
- (toto|titi): match any line containing word toto or word titi.
- ^A[c-t]*O: find line beginning by an A followed by 0 or more letters between c and t and followed by an O.’AkcO‘, ‚AO‘, ‚AdgztrhgtrhthdsfhO‘ matches this pattern.’A O‘, ‚AbO‘, ‚Acdef‘ doesn’t.
- ^A(toto|titi)*.B*O$: find line beginning by an A followed by 0 or more word toto or titi followed by 1 undefined character followed by 0 or more letter B and ending by an O.’A O‘, ‚Atototototiti BBBBBBBO‘ matches this pattern.’A Ok‘, ‚BO‘ doesn’t.