Dollar Sign Substitutions

The dollar sign is used for more than variable substitution. There are a variety of dollar expansions, some substituting string values and others mimicking capabilities of Linux commands such as wc and sed. By using the dollar sign expressions, the shell doesn't have to start these programs and will run faster.

ANSI C Escape Expansion ($')

If a dollar sign is followed by a string in single quotes, the string is searched for ANSI C escape sequences and the sequences are replaced by the corresponding characters. The acceptable escape sequences are similar to the special format escape codes used by the printf command: