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std::regex_search
Defined in header <regex> | ||
template<class BidirIt, class Alloc, class CharT, class Traits > | (1) | (since C++11) |
template<class CharT, class Alloc, class Traits > bool regex_search(const CharT* str, | (2) | (since C++11) |
template<class STraits, class SAlloc, class Alloc, class CharT, class Traits > | (3) | (since C++11) |
template<class BidirIt, class CharT, class Traits > | (4) | (since C++11) |
template<class CharT, class Traits > bool regex_search(const CharT* str, | (5) | (since C++11) |
template<class STraits, class SAlloc, class CharT, class Traits > | (6) | (since C++11) |
template<class STraits, class SAlloc, class Alloc, class CharT, class Traits > | (7) | (since C++11) |
Determines if there is a match between the regular expression e and some subsequence in the target character sequence.
[first,last). Match results are returned in m.str. Match results are returned in m.s. Match results are returned in m.match_resultsm with string iterators that become invalid immediately.regex_search will 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 |
[edit]Parameters
| first, last | - | a range identifying the target character sequence |
| str | - | a pointer to a null-terminated target character sequence |
| s | - | a string identifying target character sequence |
| e | - | the std::regex that should be applied to the target character sequence |
| m | - | the match results |
| 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. | ||
[edit]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 | 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 |
| 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 |
[edit]Notes
In order to examine all matches within the target sequence, std::regex_search may be called in a loop, restarting each time from m[0].second of the previous call. std::regex_iterator offers an easy interface to this iteration.
[edit]Example
#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})"); // simple matchfor(constauto&line : lines){std::cout<< line <<": "<<std::boolalpha<< std::regex_search(line, color_regex)<<'\n';}std::cout<<'\n'; // show contents of marked subexpressions within each matchstd::smatch color_match;for(constauto& line : lines){if(std::regex_search(line, color_match, color_regex)){std::cout<<"matches for '"<< line <<"'\n";std::cout<<"Prefix: '"<< color_match.prefix()<<"'\n";for(size_t i =0; i < color_match.size();++i)std::cout<< i <<": "<< color_match[i]<<'\n';std::cout<<"Suffix: '"<< color_match.suffix()<<"\'\n\n";}} // repeated search (see also std::regex_iterator)std::string log(R"( Speed: 366 Mass: 35 Speed: 378 Mass: 32 Speed: 400 Mass: 30)");std::regex r(R"(Speed:\t\d*)");std::smatch sm;while(regex_search(log, sm, r)){std::cout<< sm.str()<<'\n'; log = sm.suffix();} // C-style string demostd::cmatch cm;if(std::regex_search("this is a test", cm, std::regex("test")))std::cout<<"\nFound "<< cm[0]<<" at position "<< cm.prefix().length();}
Output:
Roses are #ff0000: true violets are #0000ff: true all of my base are belong to you: false matches for 'Roses are #ff0000' Prefix: 'Roses are ' 0: #ff0000 1: ff 2: 00 3: 00 Suffix: '' matches for 'violets are #0000ff' Prefix: 'violets are ' 0: #0000ff 1: 00 2: 00 3: ff Suffix: '' Speed: 366 Speed: 378 Speed: 400 Found test at position 10
[edit]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 |
[edit]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 an entire character sequence (function template) |
