std::regex_match
<regex>
bool regex_match( BidirIt first, BidirIt last,
std::match_results <BidirIt, Alloc>& m,
const std::basic_regex <CharT, Traits>& e,
std::regex_constants::match_flag_type flags =
bool regex_match( BidirIt first, BidirIt last,
const std::basic_regex <CharT, Traits>& e,
std::regex_constants::match_flag_type flags =
bool regex_match( const CharT* str,
std::match_results <const CharT*, Alloc>& m,
const std::basic_regex <CharT, Traits>& e,
std::regex_constants::match_flag_type flags =
bool regex_match( const CharT* str, const std::basic_regex <CharT, Traits>& e,
std::regex_constants::match_flag_type flags =
class CharT, class Traits >
bool regex_match
( const std::basic_string <CharT, STraits, SAlloc>& s,
std::match_results
<typename std::basic_string <CharT, STraits, SAlloc>::const_iterator,
Alloc>& m,
const std::basic_regex <CharT, Traits>& e,
std::regex_constants::match_flag_type flags =
bool regex_match( const std::basic_string <CharT, STraits, SAlloc>& s,
const std::basic_regex <CharT, Traits>& e,
std::regex_constants::match_flag_type flags =
class CharT, class Traits >
bool regex_match
( const std::basic_string <CharT, STraits, SAlloc>&&,
std::match_results
<typename std::basic_string <CharT, STraits, SAlloc>::const_iterator,
Alloc>&,
const std::basic_regex <CharT, Traits>&,
std::regex_constants::match_flag_type flags =
Determines if the regular expression e matches the entire target character sequence. The detailed match result is stored in m (if present).
[
first,
last)
.
If BidirIt
does not satisfy the requirements of LegacyBidirectionalIterator, the behavior is undefined.
If BidirIt
does not model bidirectional_iterator
, the behavior is undefined.
[
str,
str + std::char_traits <CharT>::length(str))
.If the match does not exist, the following expressions involving m (if exists) should yield the specified values:
Expression | Value |
---|---|
m.ready () | true |
m.size () | 0 |
m.empty () | true |
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:
Expression | Value | ||
---|---|---|---|
Overload (1) | Overload (3) | Overload (5) | |
m.ready () | true | ||
m.size () | 1 + e.mark_count () | ||
m.empty () | false | ||
m.prefix ().first | first | str | s.begin() |
m.prefix ().second | |||
m.prefix ().matched | false[1] | ||
m.suffix ().first | last | std::char_traits <CharT>:: length(str) + str |
s.end() |
m.suffix ().second | |||
m.suffix ().matched | false[2] | ||
m[0] .first | first | str | s.begin() |
m[0] .second | last | std::char_traits <CharT>:: length(str) + str |
s.end() |
m[0] .matched | true[3] | ||
m[n] .first |
| ||
m[n] .second |
| ||
m[n] .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 <cstddef> #include <iostream> #include <regex> #include <string> 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.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2205 | C++11 | n could be zero in the postcondition | can only be positive |
LWG 2273 | C++11 | it was unclear whether partial matches are considered | only considers full matches |
LWG 2329 | C++11 | overload (5) accepted basic_string rvalues,which could result in dangling iterators |
rejected via deleted overload (7) |
[edit] See also
(class template) [edit]
(function template) [edit]