Namespaces
Variants
Views
Actions

Difference between revisions of "cpp/regex/regex match"

From cppreference.com
< cpp‎ | regex
(rm extra spaces)
m (Shorten template names. Use {{lc}} where appropriate.)
Line 1: Line 1:
 
{{cpp/title|regex_match}}
 
{{cpp/title|regex_match}}
 
{{cpp/regex/navbar}}
 
{{cpp/regex/navbar}}
−
{{ddcl list begin}}
+
{{dcl begin}}
−
{{ddcl list header | regex}}
+
{{dcl header | regex}}
−
{{ddcl list item | num=1 | notes={{mark since c++11}} | 1=
+
{{dcl | num=1 | notes={{mark since c++11}} | 1=
 
template< class BidirIt,  
 
template< class BidirIt,  
 
           class Alloc, class CharT, class Traits >
 
           class Alloc, class CharT, class Traits >
Line 12: Line 12:
 
                       std::regex_constants::match_default );
 
                       std::regex_constants::match_default );
 
}}
 
}}
−
{{ddcl list item | num=2 | notes={{mark since c++11}} | 1=
+
{{dcl | num=2 | notes={{mark since c++11}} | 1=
 
template< class BidirIt,  
 
template< class BidirIt,  
 
           class CharT, class Traits >
 
           class CharT, class Traits >
Line 20: Line 20:
 
                       std::regex_constants::match_default );
 
                       std::regex_constants::match_default );
 
}}
 
}}
−
{{ddcl list item | num=3 | notes={{mark since c++11}} | 1=
+
{{dcl | num=3 | notes={{mark since c++11}} | 1=
 
template< class CharT, class Alloc, class Traits >
 
template< class CharT, class Alloc, class Traits >
 
bool regex_match( const CharT* str,
 
bool regex_match( const CharT* str,
Line 28: Line 28:
 
                       std::regex_constants::match_default );
 
                       std::regex_constants::match_default );
 
}}
 
}}
−
{{ddcl list item | num=4 | notes={{mark since c++11}} | 1=
+
{{dcl | num=4 | notes={{mark since c++11}} | 1=
 
template< class STraits, class SAlloc,  
 
template< class STraits, class SAlloc,  
 
           class Alloc, class CharT, class Traits >
 
           class Alloc, class CharT, class Traits >
Line 40: Line 40:
 
                       std::regex_constants::match_default );
 
                       std::regex_constants::match_default );
 
}}
 
}}
−
{{ddcl list item | num=5 | notes={{mark since c++11}} | 1=
+
{{dcl | num=5 | notes={{mark since c++11}} | 1=
 
template< class CharT, class Traits >
 
template< class CharT, class Traits >
 
bool regex_match( const CharT* str,
 
bool regex_match( const CharT* str,
Line 47: Line 47:
 
                       std::regex_constants::match_default );
 
                       std::regex_constants::match_default );
 
}}
 
}}
−
{{ddcl list item | num=6 | notes={{mark since c++11}} | 1=
+
{{dcl | num=6 | notes={{mark since c++11}} | 1=
 
template< class STraits, class SAlloc,  
 
template< class STraits, class SAlloc,  
 
           class CharT, class Traits >
 
           class CharT, class Traits >
Line 55: Line 55:
 
                       std::regex_constants::match_default );
 
                       std::regex_constants::match_default );
 
}}
 
}}
−
{{ddcl list end}}
+
{{dcl end}}
  
 
1) Determines if there is a match between the regular expression {{tt|e}} and the entire target character sequence {{tt|[first,last)}}, taking into account the effect of {{tt|flags}}. Match results are returned in {{tt|m}}.
 
1) Determines if there is a match between the regular expression {{tt|e}} and the entire target character sequence {{tt|[first,last)}}, taking into account the effect of {{tt|flags}}. Match results are returned in {{tt|m}}.
Line 69: Line 69:
 
6) Returns {{c|std::regex_match(s.begin(), s.end(), e, flags)}}.
 
6) Returns {{c|std::regex_match(s.begin(), s.end(), e, flags)}}.
  
−
Note that {{tt|regex_match}} will only successfully match a regular expression to an ''entire'' character sequence, whereas {{c|std::regex_search}} will successfully match subsequences.
+
Note that {{tt|regex_match}} will only successfully match a regular expression to an ''entire'' character sequence, whereas {{lc|std::regex_search}} will successfully match subsequences.
  
 
===Parameters===
 
===Parameters===
−
{{param list begin}}
+
{{par begin}}
−
{{param list item | first, last | the target character range to apply the regex to, given as iterators}}
+
{{par | first, last | the target character range to apply the regex to, given as iterators}}
−
{{param list item | m | the match results}}
+
{{par | m | the match results}}
−
{{param list item | str | the target string, given as a null-terminated C-style string}}
+
{{par | str | the target string, given as a null-terminated C-style string}}
−
{{param list item | s | the target string, given as a {{c|std::basic_string}} }}
+
{{par | s | the target string, given as a {{lc|std::basic_string}} }}
−
{{param list item | e | the regular expression}}
+
{{par | e | the regular expression}}
−
{{param list item | flags | flags used to determine how the match will be performed}}
+
{{par | flags | flags used to determine how the match will be performed}}
−
{{param list hreq}}
+
{{par hreq}}
−
{{param list req concept | BidirIt | BidirectionalIterator}}
+
{{par req concept | BidirIt | BidirectionalIterator}}
−
{{param list end}}
+
{{par end}}
  
 
===Return value===
 
===Return value===
Line 87: Line 87:
  
 
If the match does not exist:
 
If the match does not exist:
−
{{dcl list begin}}
+
{{dsc begin}}
−
{{dcl list item | {{c|1=m.ready() == true}} }}
+
{{dsc | {{c|1=m.ready() == true}} }}
−
{{dcl list item | {{c|1=m.empty() == true}} }}
+
{{dsc | {{c|1=m.empty() == true}} }}
−
{{dcl list item | {{c|1=m.size() == 0}} }}
+
{{dsc | {{c|1=m.size() == 0}} }}
−
{{dcl list end}}
+
{{dsc end}}
  
 
If the match exists:
 
If the match exists:
−
{{dcl list begin}}
+
{{dsc begin}}
−
{{dcl list item | {{c|m.ready()}} | {{c|true}} }}
+
{{dsc | {{c|m.ready()}} | {{c|true}} }}
−
{{dcl list item | {{c|m.empty()}} | {{c|false}} }}
+
{{dsc | {{c|m.empty()}} | {{c|false}} }}
−
{{dcl list item | {{c|m.size()}}  | number of subexpressions plus 1, that is, {{c|1+e.mark_count()}}}}
+
{{dsc | {{c|m.size()}}  | number of subexpressions plus 1, that is, {{c|1+e.mark_count()}}}}
−
{{dcl list item | {{c|m.prefix().first}} | {{tt|first}} }}
+
{{dsc | {{c|m.prefix().first}} | {{tt|first}} }}
−
{{dcl list item | {{c|m.prefix().second}} | {{tt|first}} }}
+
{{dsc | {{c|m.prefix().second}} | {{tt|first}} }}
−
{{dcl list item | {{c|m.prefix().matched}} | {{c|false}} (the match prefix is empty) }}
+
{{dsc | {{c|m.prefix().matched}} | {{c|false}} (the match prefix is empty) }}
−
{{dcl list item | {{c|m.suffix().first}} | {{tt|last}}}}
+
{{dsc | {{c|m.suffix().first}} | {{tt|last}}}}
−
{{dcl list item | {{c|m.suffix().second}} | {{tt|last}}}}
+
{{dsc | {{c|m.suffix().second}} | {{tt|last}}}}
−
{{dcl list item | {{c|m.suffix().matched}} | {{c|false}} (the match suffix is empty) }}
+
{{dsc | {{c|m.suffix().matched}} | {{c|false}} (the match suffix is empty) }}
−
{{dcl list item | {{c|m[0].first}} | {{tt|first}} }}
+
{{dsc | {{c|m[0].first}} | {{tt|first}} }}
−
{{dcl list item | {{c|m[0].second}} | {{tt|last}} }}
+
{{dsc | {{c|m[0].second}} | {{tt|last}} }}
−
{{dcl list item | {{c|m[0].matched}} | {{c|true}} (the entire sequence is matched)}}
+
{{dsc | {{c|m[0].matched}} | {{c|true}} (the entire sequence is matched)}}
−
{{dcl list item | {{c|1=m[n].first}} | the start of the sequence that matched sub-expression n, or {{tt|last}} if the subexpression did not participate in the match}}
+
{{dsc | {{c|1=m[n].first}} | the start of the sequence that matched sub-expression n, or {{tt|last}} if the subexpression did not participate in the match}}
−
{{dcl list item | {{c|1=m[n].second}} | the end of the sequence that matched sub-expression n, or {{tt|last}} if the subexpression did not participate in the match}}
+
{{dsc | {{c|1=m[n].second}} | the end of the sequence that matched sub-expression n, or {{tt|last}} if the subexpression did not participate in the match}}
−
{{dcl list item | {{c|1=m[n].matched}} | {{c|true}} if sub-expression n participated in the match, {{c|false}} otherwise}}
+
{{dsc | {{c|1=m[n].matched}} | {{c|true}} if sub-expression n participated in the match, {{c|false}} otherwise}}
−
{{dcl list end}}
+
{{dsc end}}
  
 
===Example===
 
===Example===
Line 182: Line 182:
  
 
===See also===
 
===See also===
−
{{dcl list begin}}
+
{{dsc begin}}
−
{{dcl list template | cpp/regex/dcl list basic_regex}}
+
{{dsc inc | cpp/regex/dcl list basic_regex}}
−
{{dcl list template | cpp/regex/dcl list match_results}}
+
{{dsc inc | cpp/regex/dcl list match_results}}
−
{{dcl list template | cpp/regex/dcl list regex_search}}
+
{{dsc inc | cpp/regex/dcl list regex_search}}
−
{{dcl list end}}
+
{{dsc end}}
  
 
[[de:cpp/regex/regex match]]
 
[[de:cpp/regex/regex match]]

Revision as of 19:52, 31 May 2013

 
C++
 
Regular expressions library
Classes
(C++11)
(C++11)
(C++11)
Algorithms
regex_match
(C++11)
(C++11)
(C++11)
Iterators
(C++11)
(C++11)
Exceptions
(C++11)
Traits
(C++11)
Constants
(C++11)
(C++11)
(C++11)
Regex Grammar
(C++11)
 
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)

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).

Note that regex_match will only successfully match a regular expression to an entire character sequence, whereas std::regex_search will successfully match subsequences.

Contents

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

Template:par req concept

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", "baz.dat", "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';
            }
        }
    }
 
    // Extraction of several sub-matches
    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

See also

Template:cpp/regex/dcl list basic regexTemplate:cpp/regex/dcl list match resultsTemplate:cpp/regex/dcl list regex search
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/regex/regex_match&oldid=51140"