Emacs Advent Calendar 10: Searching

Thu 2015-12-10

Emacs of course has commands to search for occurences of strings.

The normal mode of operation is an incremental search which can be performed forwards (C-s) or backward (C-r). Those two commands prompt for a string to search. Repeated invocations of either C-s or C-r jump to the next or previous match respectively. Note that you can change direction in mid-search.

Nearly all other commands, especially RET and all movement commands, cancel a search. To repeat a canceled search with the last search string, press C-s C-s or C-r C-r.

Searches start from point. If a search fails at the end of a buffer, another press of C-s starts the search again from the beginning of the buffer. Emacs displays Wrapped in the echo area. If the search passes the original location of point, Emacs will display Overwrapped.

To include a literal newline in the search string, enter it by pressing C-j.

To edit the search string, press M-e. To get back to an earlier search string, use M-n and M-p to cycle through the search ring (similar to the minibuffer command ring).

Entries from the kill ring can be inserted to the search string by yanking them with C-y.

A very handy feature when searching for words that might be separated by a newline character (e.g. in texts that are filled to a width of N characters) is word search. To start word search or to toggle word search mode from an active incremental search, press M-s w.

To switch from incremental searching to an interactive search and replace operation, press M-% (more on this later).

There are some special rules for searching one should be aware of to not be surprised in cases where this is not the intended behavior:

  • Incremental search performs lax space matching, i.e. each sequence of spaces in the search string matches any sequence of one or more spaces in the text. This can be toggled by M-SPC.
  • If a search string contains only characters in lower case, matching will be performed case insensitive. To toggle case sensitivity during an incremental search, press M-c .

For more information see sections 15.1 (Incremental Search), 15.3 (Word Search) and 15.9 (Searching and Case) of the Emacs Reference Manual.

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This text by Ludger Sandig is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.