std::regex_match - cppreference.com (original) (raw)

Determines if the regular expression e matches the entire target character sequence. The detailed match result is stored in m (if present).

1,2) The target character sequence is represented by the range [first, last).

3,4) The target character sequence is represented by the range [str, str + std::char_traits<CharT>::length(str)).

5,6) The target character sequence is represented by the string s.

1. The target character sequence cannot be represented by a std::string rvalue.

If the match does not exist, the following expressions involving m (if exists) should yield the specified values:

If the match exists, given any integer in (​0, m.size()) as n, the following expressions involving m should yield the specified values for each overload listed below:

1. ↑ The match prefix is empty.
2. ↑ The match suffix is empty.
3. ↑ The entire sequence is matched.

[edit] Parameters

[edit] Return value

Returns true if the entire target sequence matches e, false otherwise.

[edit] Notes

Because regex_match only considers full matches, the same regex may give different matches between regex_match and std::regex_search:

std::regex re("Get|GetValue"); std::cmatch m; std::regex_search("GetValue", m, re); // returns true, and m[0] contains "Get" std::regex_match ("GetValue", m, re); // returns true, and m[0] contains "GetValue" std::regex_search("GetValues", m, re); // returns true, and m[0] contains "Get" std::regex_match ("GetValues", m, re); // returns false

[edit] Example

#include #include #include #include   int main() { // Simple regular expression matching const std::string fnames[] = {"foo.txt", "bar.txt", "baz.dat", "zoidberg"}; const std::regex txt_regex("[a-z]+\.txt");   for (const auto& fname : fnames) std::cout << fname << ": " << std::regex_match(fname, txt_regex) << '\n';   // Extraction of a sub-match const std::regex base_regex("([a-z]+)\.txt"); std::smatch base_match;   for (const auto& fname : fnames) if (std::regex_match(fname, base_match, base_regex)) // The first sub_match is the whole string; the next // sub_match is the first parenthesized expression. if (base_match.size() == 2) { std::ssub_match base_sub_match = base_match[1]; std::string base = base_sub_match.str(); std::cout << fname << " has a base of " << base << '\n'; }   // Extraction of several sub-matches const std::regex pieces_regex("([a-z]+)\.([a-z]+)"); std::smatch pieces_match;   for (const auto& fname : fnames) if (std::regex_match(fname, pieces_match, pieces_regex)) { std::cout << fname << '\n'; for (std::size_t i = 0; i < pieces_match.size(); ++i) { std::ssub_match sub_match = pieces_match[i]; std::string piece = sub_match.str(); std::cout << " submatch " << i << ": " << piece << '\n'; } } }

Output:

foo.txt: 1 bar.txt: 1 baz.dat: 0 zoidberg: 0 foo.txt has a base of foo bar.txt has a base of bar foo.txt submatch 0: foo.txt submatch 1: foo submatch 2: txt bar.txt submatch 0: bar.txt submatch 1: bar submatch 2: txt baz.dat submatch 0: baz.dat submatch 1: baz submatch 2: dat

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also

| | regular expression object (class template) [edit] | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | identifies one regular expression match, including all sub-expression matches (class template) [edit] | | | attempts to match a regular expression to any part of a character sequence (function template) [edit] |