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34.1 Searching for Strings

These are the primitive functions for searching through the text in a buffer. They are meant for use in programs, but you may call them interactively. If you do so, they prompt for the search string; the arguments limit and noerror are nil, and repeat is 1. For more details on interactive searching, see Searching and Replacement.

These search functions convert the search string to multibyte if the buffer is multibyte; they convert the search string to unibyte if the buffer is unibyte. See Text Representations.

— Command: search-forward string &optional limit noerror count

This function searches forward from point for an exact match for string. If successful, it sets point to the end of the occurrence found, and returns the new value of point. If no match is found, the value and side effects depend on noerror (see below).

In the following example, point is initially at the beginning of the line. Then (search-forward "fox") moves point after the last letter of ‘fox’: 

          ---------- Buffer: foo ----------
          -!-The quick brown fox jumped over the lazy dog.
          ---------- Buffer: foo ----------
          
          (search-forward "fox")
               ⇒ 20
          
          ---------- Buffer: foo ----------
          The quick brown fox-!- jumped over the lazy dog.
          ---------- Buffer: foo ----------

The argument limit specifies the bound to the search, and should be a position in the current buffer. No match extending after that position is accepted. If limit is omitted or nil, it defaults to the end of the accessible portion of the buffer.

What happens when the search fails depends on the value of noerror. If noerror is nil, a search-failed error is signaled. If noerror is t, search-forward returns nil and does nothing. If noerror is neither nil nor t, then search-forward moves point to the upper bound and returns nil.

The argument noerror only affects valid searches which fail to find a match. Invalid arguments cause errors regardless of noerror.

If count is a positive number n, the search is done n times; each successive search starts at the end of the previous match. If all these successive searches succeed, the function call succeeds, moving point and returning its new value. Otherwise the function call fails, with results depending on the value of noerror, as described above. If count is a negative number −n, the search is done n times in the opposite (backward) direction.

— Command: search-backward string &optional limit noerror count

This function searches backward from point for string. It is like search-forward, except that it searches backwards rather than forwards. Backward searches leave point at the beginning of the match.

— Command: word-search-forward string &optional limit noerror count

This function searches forward from point for a word match for string. If it finds a match, it sets point to the end of the match found, and returns the new value of point.

Word matching regards string as a sequence of words, disregarding punctuation that separates them. It searches the buffer for the same sequence of words. Each word must be distinct in the buffer (searching for the word ‘ball’ does not match the word ‘balls’), but the details of punctuation and spacing are ignored (searching for ‘ball boy’ does match ‘ball. Boy!’).

In this example, point is initially at the beginning of the buffer; the search leaves it between the ‘y’ and the ‘!’. 

          ---------- Buffer: foo ----------
          -!-He said "Please!  Find
          the ball boy!"
          ---------- Buffer: foo ----------
          
          (word-search-forward "Please find the ball, boy.")
               ⇒ 39
          
          ---------- Buffer: foo ----------
          He said "Please!  Find
          the ball boy-!-!"
          ---------- Buffer: foo ----------

If limit is non-nil, it must be a position in the current buffer; it specifies the upper bound to the search. The match found must not extend after that position.

If noerror is nil, then word-search-forward signals an error if the search fails. If noerror is t, then it returns nil instead of signaling an error. If noerror is neither nil nor t, it moves point to limit (or the end of the accessible portion of the buffer) and returns nil.

If count is a positive number, it specifies how many successive occurrences to search for. Point is positioned at the end of the last match. If count is a negative number, the search is backward and point is positioned at the beginning of the last match.

Internally, word-search-forward and related functions use the function word-search-regexp to convert string to a regular expression that ignores punctuation.

— Command: word-search-forward-lax string &optional limit noerror count

This command is identical to word-search-forward, except that the beginning or the end of string need not match a word boundary, unless string begins or ends in whitespace. For instance, searching for ‘ball boy’ matches ‘ball boyee’, but does not match ‘balls boy’.

— Command: word-search-backward string &optional limit noerror count

This function searches backward from point for a word match to string. This function is just like word-search-forward except that it searches backward and normally leaves point at the beginning of the match.

— Command: word-search-backward-lax string &optional limit noerror count

This command is identical to word-search-backward, except that the beginning or the end of string need not match a word boundary, unless string begins or ends in whitespace.