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.