Linux Shell Scripting Cookbook - Third Edition

Identifiers

Identifiers are the basis of regular expressions. These define the characters that must be present (or absent) to match the regular expression.

regex	Description	Example
A character	The regular expression must match this letter.	A will match the letter A
.	This matches any one character.	"Hack." matches Hack1, Hacki, but not Hack12 or Hackil; only one additional character matches
[]	This matches any one of the characters enclosed in the brackets. The enclosed characters may be a set or a range.	coo[kl] matches cook or cool; [0-9] matches any single digit
[^]	This matches any one of the characters except those that are enclosed in square brackets. The enclosed characters may be a set or a ...