Wildcards are used on the shell command line to specify files by name or extension. Shells for Linux offer sophisticated forms of wildcards that you can use to perform complex pattern matching. Creating complex wildcards is called building regular expressions.
Regular expressions are wildcard patterns, built using a special command-line syntax. This syntax uses a number of special characters, some of which are listed in Table 2.2.
|*||Match all characters|
|?||Match a single character|
|[a–z]||Match a range of characters|
|||Match a range of characters|
|\ ?||Match the ? character|
|\ )||Match the ) character|
|^abc||Match pattern ...|