Egrep Patterns

The escape character is a backslash (\). You can use it to escape meta characters to use them in their plain character form.

In the following examples literal 'E' and 'F' denote any expression, whether a pattern or a character.

(: Start a capturing subexpression.
): End a capturing subexpression.
E|F: Disjunction, match either E or F (inclusive). E is preferred if both match.
E*: Act as Kleene star, match E zero or more times.
E+: Closure, match E one or more times.
E?: Option, match E optionally once.
.: Match any character except for newline characters (\n, \f, \r) and the NULL byte.
E{n}: Match E exactly n times.
E{n,} or E{n,0}: Match E n or more times.
E{,n} or E{0,n}: Match E at most n times.
E{n,m}: Match E no less than n times and no more than m times.
[: Start a character set, see Character Sets For Egrep.
$: Match the empty string at the end of the input or at the end of a line.
^: Match the empty string at the start of the input or at the beginning of a line.