std::regex_match

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Regular expressions library

Classes

basic_regex (C++11)

sub_match (C++11)

match_results (C++11)

Algorithms

regex_match (C++11)

regex_search (C++11)

regex_replace (C++11)

Iterators

regex_iterator (C++11)

regex_token_iterator (C++11)

Exceptions

regex_error (C++11)

Traits

regex_traits (C++11)

Constants

syntax_option_type (C++11)

match_flag_type (C++11)

error_type (C++11)

Regex Grammar

Modified ECMAScript-262 (C++11)

 

Template:ddcl list begin <tr class="t-dsc-header">

<td>

Defined in header <regex>

</td>

<td></td> <td></td> </tr> <tr class="t-dcl ">

<td >

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 );

</td>

<td > (1) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

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 );

</td>

<td > (2) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

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 );

</td>

<td > (3) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

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 );

</td>

<td > (4) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

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 );

</td>

<td > (5) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

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 );

</td>

<td > (6) </td> <td > (since C++11) </td> </tr> Template:ddcl list end

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. 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).

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 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 sub-expression n, or last if the subexpression did not participate in the match
m[n].second	the end of the sequence that matched 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

Example

Run this code

#include <iostream>
#include <string>
#include <regex>
 
int main()
{
    // Simple regular expression matching
    std::string fnames[] = {"foo.txt", "bar.txt", "zoidberg"};
    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                                                            
    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';
            }   
        }   
    }
}

Output:

foo.txt: 1
bar.txt: 1
zoidberg: 0
foo.txt has a base of foo
bar.txt has a base of bar

See also

Template:cpp/regex/dcl list basic regexTemplate:cpp/regex/dcl list match results