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

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< cpp‎ | regex
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Line 116: Line 116:
 
{{example
 
{{example
 
  | code=
 
  | code=
 +
#include <iostream>
 +
#include <string>
 +
#include <regex>
 +
 +
int main()
 +
{
 +
    std::string lines[] = {"Roses are #ff0000",
 +
                          "violets are #0000ff",
 +
                          "all of my base are belong to you"};
 +
 +
    std::regex color_regex("#([a-f0-9]{2})"
 +
                            "([a-f0-9]{2})"
 +
                            "([a-f0-9]{2})");
 +
 +
    for (const auto &line : lines) {
 +
        std::cout << line << ": "
 +
                  << std::regex_search(line, color_regex) << '\n';
 +
    } 
 +
   
 +
    std::smatch color_match;
 +
    for (const auto &line : lines) {
 +
        std::regex_search(line, color_match, color_regex);
 +
        std::cout << "matches for '" << line << "'\n";
 +
        for (size_t i = 0; i < color_match.size(); ++i) {
 +
            std::ssub_match sub_match = color_match[i];
 +
            std::string sub_match_str = sub_match.str();
 +
            std::cout << i << ": " << sub_match_str << '\n';
 +
        } 
 +
    } 
 +
}
 
  | output=
 
  | output=
 +
Roses are #ff0000: 1
 +
violets are #0000ff: 1
 +
all of my base are belong to you: 0
 +
matches for 'Roses are #ff0000'
 +
0: #ff0000
 +
1: ff
 +
2: 00
 +
3: 00
 +
matches for 'violets are #0000ff'
 +
0: #0000ff
 +
1: 00
 +
2: 00
 +
3: ff
 +
matches for 'all of my base are belong to you'
 
}}
 
}}
  

Revision as of 12:21, 14 January 2013

 
C++
 
Regular expressions library
Classes
(C++11)
(C++11)
(C++11)
Algorithms
(C++11)
regex_search
(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)
 

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_search( 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 Alloc, class CharT, class Traits >

bool regex_search( const CharT* str,
                   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 > (2) </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_search( 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 > (3) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >
template< class BidirIt,

          class CharT, class Traits >
bool regex_search( 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 > (4) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >
template< class CharT, class Traits >

bool regex_search( 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_search( 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 express e and some subsequence in the target character sequence [first,last). Match results are returned in m.

2) Returns std::regex_search(str, str + std::char_traits<CharT>::length(str), m, e, flags).

3) Returns std::regex_search(s.begin(), s.end(), m, e, flags).

4) The same as (1), omitting the match results.

5) Returns std::regex_search(str, str + std::char_traits<CharT>::length(str), e, flags).

6) Returns std::regex_search(s.begin(), s.end(), e, flags).

Note that regex_search can successfully match any subsequence of the given sequence, whereas std::regex_match will only return true if the regular expression matches the entire sequence.

Contents

Parameters

first, last - the target character range
m - the match results
str - a target null-terminated C-style string
s - a target std::basic_string
e - the std::regex that should be applied to the target
flags - std::regex_constants::match_flag_type governing search behavior
Type requirements
-
BidirIt must meet the requirements of LegacyBidirectionalIterator.
-
Alloc must meet the requirements of Allocator.

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 m[0].first
m.prefix().matched m.prefix().first != m.prefix().second
m.suffix().first m[0].second
m.suffix().second last
m.suffix().matched m.suffix().first != m.suffix().second
m[0].first the start of the matching sequence
m[0].second the end of the matching sequence
m[0].matched true if a match was found, false otherwise
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()
{
    std::string lines[] = {"Roses are #ff0000",
                           "violets are #0000ff",
                           "all of my base are belong to you"};
 
    std::regex color_regex("#([a-f0-9]{2})"
                            "([a-f0-9]{2})"
                            "([a-f0-9]{2})");
 
    for (const auto &line : lines) {
        std::cout << line << ": " 
                  << std::regex_search(line, color_regex) << '\n';
    }   
 
    std::smatch color_match;
    for (const auto &line : lines) {
        std::regex_search(line, color_match, color_regex);
        std::cout << "matches for '" << line << "'\n";
        for (size_t i = 0; i < color_match.size(); ++i) {
            std::ssub_match sub_match = color_match[i];
            std::string sub_match_str = sub_match.str();
            std::cout << i << ": " << sub_match_str << '\n';
        }   
    }   
}

Output: 

Roses are #ff0000: 1
violets are #0000ff: 1
all of my base are belong to you: 0
matches for 'Roses are #ff0000'
0: #ff0000
1: ff
2: 00
3: 00
matches for 'violets are #0000ff'
0: #0000ff
1: 00
2: 00
3: ff
matches for 'all of my base are belong to you'

See also

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