34.6 The Match Data

Emacs keeps track of the start and end positions of the segments of text found during a regular expression search. This means, for example, that you can search for a complex pattern, such as a date in an Rmail message, and then extract parts of the match under control of the pattern.

Because the match data normally describe the most recent search only, you must be careful not to do another search inadvertently between the search you wish to refer back to and the use of the match data. If you can't avoid another intervening search, you must save and restore the match data around it, to prevent it from being overwritten.

34.6.1 Replacing the Text that Matched		Replacing a substring that was matched.
34.6.2 Simple Match Data Access		Accessing single items of match data, such as where a particular subexpression started.
34.6.3 Accessing the Entire Match Data		Accessing the entire match data at once, as a list.
34.6.4 Saving and Restoring the Match Data		Saving and restoring the match data.