std::regex_match (3) Linux Manual Page
std::regex_match – std::regex_match
Synopsis
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, (1)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class BidirIt,
class CharT, class Traits>
bool regex_match(BidirIt first, BidirIt last, (2)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class CharT, class Alloc, class Traits>
bool regex_match(const CharT *str,
std::match_results<const CharT *, Alloc> &m, (3)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
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, (4)(since C++ 11)
Alloc
> &m,
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class CharT, class Traits>
bool regex_match(const CharT *str,
const std::basic_regex<CharT, Traits> &e, (5)(since C++ 11)
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class STraits, class SAlloc,
class CharT, class Traits>
bool regex_match(const std::basic_string<CharT, STraits, SAlloc> &s, (6)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
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, (7)(since C++ 14)
Alloc
> &,
const std::basic_regex<CharT, Traits> &,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default) = delete;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.
1) Determines if there is a match between the regular expression 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.
2) Behaves as (1) above, omitting the match results.
3) Returns std::regex_match(str, str + std::char_traits<charT>::length(str), m, e, flags).
4) Returns std::regex_match(s.begin(), s.end(), m, e, flags).
5) Returns std::regex_match(str, str + std::char_traits<charT>::length(str), e, flags).
6) Returns std::regex_match(s.begin(), s.end(), e, flags).
7) The overload 4 is prohibited from accepting temporary strings, otherwise this function populates 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:
Example
// Run this code
#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:
See also
basic_regex regular expression object
(C++11)
match_results identifies one regular expression match, including all sub-expression matches
(C++11)
regex_search attempts to match a regular expression to any part of a character sequence
(C++11)