3.3 The Backslash Character and Special Expressions
The ‘\’ character,
when followed by certain ordinary characters,
takes a special meaning:
- ‘\b’
- Match the empty string at the edge of a word.
- ‘\B’
- Match the empty string provided it's not at the edge of a word.
- ‘\<’
- Match the empty string at the beginning of word.
- ‘\>’
- Match the empty string at the end of word.
- ‘\w’
- Match word constituent, it is a synonym for ‘[_[:alnum:]]’.
- ‘\W’
- Match non-word constituent, it is a synonym for ‘[^_[:alnum:]]’.
- ‘\s’
- Match whitespace, it is a synonym for ‘[[:space:]]’.
- ‘\S’
- Match non-whitespace, it is a synonym for ‘[^[:space:]]’.
For example, ‘\brat\b’ matches the separate word ‘rat’,
‘\Brat\B’ matches ‘crate’ but not ‘furry rat’.