1 Characters that must be escaped

He Diyi edited this page 2019-10-04 23:06:28 +08:00

Outside of a class, ^$.?*+()[\| must be escaped to be used literally.

Inside of a class, \[]^- must be escaped to be used literally. This deserves a bit of clarification:

• [ must be escaped to be used literally because it denotes the start of a set in a class.
• Unescaped ] can be used literally when it is placed at the very beginning of a class.
• Unescaped ^ can be used literally when it is not placed at the beginning of a class.
• Unescaped - can be used literally when it is placed at the beginning or end of a class.

In extended mode, # becomes a metacharacter denoting the start of a comment, so it must be escaped to be used literally.