std::regex_match
Defined in header <regex> |
||
---|---|---|
template< class BidirIt, class Alloc, class CharT, class Traits > 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 = std::regex_constants::match_default ); |
(1) | (since C++11) |
template< class BidirIt, class CharT, class Traits > bool regex_match( BidirIt first, BidirIt last, const std::basic_regex<CharT,Traits>& e, std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); |
(2) | (since C++11) |
template< class CharT, class Alloc, class Traits > 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 = std::regex_constants::match_default ); |
(3) | (since C++11) |
template< class STraits, class SAlloc, class Alloc, 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 = std::regex_constants::match_default ); |
(4) | (since C++11) |
template< class CharT, class Traits > bool regex_match( const CharT* str, const std::basic_regex<CharT,Traits>& e, std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); |
(5) | (since C++11) |
template< class STraits, class SAlloc, class CharT, class Traits > 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 = std::regex_constants::match_default ); |
(6) | (since C++11) |
template< class STraits, class SAlloc, class Alloc, 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 = std::regex_constants::match_default ) = delete; |
(7) | (since C++11) |
Determines if the regular expression e
matches the entire target character sequence, which may be specified as std::string
, a C-string, or an iterator pair.
e
and the entire target character sequence
[first,last)
, taking into account the effect of
flags
. When determining if there is a match, only potential matches that match the entire character sequence are considered. Match results are returned in
m
.
std::regex_match(str, str + std::char_traits<charT>::length(str), m, e, flags)
.
std::regex_match(s.begin(), s.end(), m, e, flags)
.
std::regex_match(str, str + std::char_traits<charT>::length(str), e, flags)
.
std::regex_match(s.begin(), s.end(), e, flags)
.
match_results
m
with string iterators that become invalid immediately.
Note that regex_match
will only successfully match a regular expression to an entire character sequence, whereas std::regex_search
will successfully match subsequences.
Parameters
first, last | - | the target character range to apply the regex to, given as iterators |
m | - | the match results |
str | - | the target string, given as a null-terminated C-style string |
s | - | the target string, given as a std::basic_string |
e | - | the regular expression |
flags | - | flags used to determine how the match will be performed |
Type requirements | ||
-BidirIt must meet the requirements of LegacyBidirectionalIterator. |
Return value
Returns true
if a match exists, false
otherwise. In either case, the object m
is updated, as follows:
If the match does not exist:
m.ready() == true |
|
m.empty() == true |
|
m.size() == 0 |
If the match exists:
m.ready() |
true |
m.empty() |
false |
m.size() |
number of marked subexpressions plus 1, that is, 1+e.mark_count() |
m.prefix().first |
first |
m.prefix().second |
first |
m.prefix().matched |
false (the match prefix is empty) |
m.suffix().first |
last |
m.suffix().second |
last |
m.suffix().matched |
false (the match suffix is empty) |
m[0].first |
first |
m[0].second |
last |
m[0].matched |
true (the entire sequence is matched) |
m[n].first |
the start of the sequence that matched marked sub-expression n, or last if the subexpression did not participate in the match |
m[n].second |
the end of the sequence that matched marked sub-expression n, or last if the subexpression did not participate in the match |
m[n].matched |
true if sub-expression n participated in the match, false otherwise |
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
Example
#include <iostream> #include <string> #include <regex> 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 (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
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 2329 | C++11 | basic_string rvalues were accepted, which was likely to result in dangling iterators |
rejected via a deleted overload |
See also
(C++11)
|
regular expression object (class template) |
(C++11)
|
identifies one regular expression match, including all sub-expression matches (class template) |
(C++11)
|
attempts to match a regular expression to any part of a character sequence (function template) |
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