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GNU Searching

Searching means trying to match starting at successive positions within a string. The function re_search does this.

Before calling re_search, you must compile your regular expression. See section GNU Regular Expression Compiling.

Here is the function declaration:

int 
re_search (struct re_pattern_buffer *pattern_buffer, 
           const char *string, const int size, 
           const int start, const int range, 
           struct re_registers *regs)

whose arguments are the same as those to re_match (see section GNU Matching) except that the two arguments start and range replace re_match's argument start.

If range is positive, then re_search attempts a match starting first at index start, then at @math{start + 1} if that fails, and so on, up to @math{start + range}; if range is negative, then it attempts a match starting first at index start, then at @math{start -1} if that fails, and so on.

If start is not between zero and size, then re_search returns @math{-1}. When range is positive, re_search adjusts range so that @math{start + range - 1} is between zero and size, if necessary; that way it won't search outside of string. Similarly, when range is negative, re_search adjusts range so that @math{start + range + 1} is between zero and size, if necessary.

If the fastmap field of pattern_buffer is zero, re_search matches starting at consecutive positions; otherwise, it uses fastmap to make the search more efficient. See section Searching with Fastmaps.

If no match is found, re_search returns @math{-1}. If a match is found, it returns the index where the match began. If an internal error happens, it returns @math{-2}.

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