| Localization library | |||||||||||||||||||||||||
| Regular expressions library(C++11) | |||||||||||||||||||||||||
| Formatting library(C++20) | |||||||||||||||||||||||||
| Null-terminated sequence utilities | |||||||||||||||||||||||||
| Byte strings | |||||||||||||||||||||||||
| Multibyte strings | |||||||||||||||||||||||||
| Wide strings | |||||||||||||||||||||||||
| Primitive numeric conversions | |||||||||||||||||||||||||
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| Text encoding identifications | |||||||||||||||||||||||||
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| Classes | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
| Algorithms | ||||
(C++11) | ||||
regex_search (C++11) | ||||
(C++11) | ||||
| Iterators | ||||
(C++11) | ||||
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| Exceptions | ||||
(C++11) | ||||
| Traits | ||||
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| Constants | ||||
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| Regex Grammar | ||||
(C++11) |
Defined in header <regex> | ||
template<class BidirIt,class Alloc,class CharT,class Traits> bool regex_search( BidirIt first, BidirIt last, | (1) | (since C++11) |
template<class BidirIt,class CharT,class Traits> bool regex_search( BidirIt first, BidirIt last, | (2) | (since C++11) |
template<class CharT,class Alloc,class Traits> bool regex_search(const CharT* str, | (3) | (since C++11) |
template<class CharT,class Traits> bool regex_search(const CharT* str,conststd::basic_regex<CharT, Traits>& e, | (4) | (since C++11) |
template<class STraits,class SAlloc,class Alloc, class CharT,class Traits> | (5) | (since C++11) |
template<class STraits,class SAlloc,class CharT,class Traits> bool regex_search(conststd::basic_string<CharT, STraits, SAlloc>& s, | (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 expressione and some subsequence in the target character sequence. The detailed match result is stored inm (if present).
[first, last).If | (until C++23) |
If | (since C++23) |
[str, str+std::char_traits<CharT>::length(str)).If a match does not exist, the following expressions involvingm (if exists) should yield the specified values:
| Expression | Value |
|---|---|
| m.ready() | true |
| m.size() | 0 |
| m.empty() | true |
If a match exists, given any integer in(0, m.size()) asn, the following expressions involvingm should yield the specified values for each overload listed below:
| Expression | Value | ||
|---|---|---|---|
| Overload(1) | Overload(3) | Overload(5) | |
| m.ready() | true | ||
| m.size() | 1+ e.mark_count() | ||
| m.empty() | false | ||
| m.prefix().first | first | str | s.begin() |
| 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 | std::char_traits<CharT>:: length(str)+ str | s.end() |
| m.suffix().matched | m.suffix().first!= m.suffix().second | ||
| m[0].first | the start of the sequence that matchede | ||
| m[0].second | the end of the sequence that matchede | ||
| m[0].matched | true | ||
| m[n].first |
| ||
| m[n].second |
| ||
| m[n].matched |
| ||
Contents |
| first, last | - | the target character range |
| str | - | the target null-terminated C-style string |
| s | - | the targetstd::basic_string |
| m | - | the match results |
| e | - | the regular expression |
| flags | - | flags used to determine how the match will be performed |
Returnstrue if a match exists,false otherwise.
In order to examine all matches within the target sequence,std::regex_search may be called in a loop, restarting each time fromm[0].second of the previous call.std::regex_iterator offers an easy interface to this iteration.
#include <cstddef>#include <iostream>#include <regex>#include <string> 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(std::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:400Mass:30)");std::regex r(R"(Speed:\t\d*)");for(std::smatch sm; 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()<<'\n';}
Output:
Roses are #ff0000: trueviolets are #0000ff: trueall of my base are belong to you: false matches for 'Roses are #ff0000'Prefix: 'Roses are '0: #ff00001: ff2: 003: 00Suffix: '' matches for 'violets are #0000ff'Prefix: 'violets are '0: #0000ff1: 002: 003: ffSuffix: '' Speed:366Speed:378Speed:400 Found test at position 10
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2205 | C++11 | n could be zero in the postcondition | can only be positive |
| LWG 2329 | C++11 | overload(5) acceptedbasic_string rvalues,which could result in dangling iterators | rejected via deleted overload(7) |
(C++11) | regular expression object (class template)[edit] |
(C++11) | identifies one regular expression match, including all sub-expression matches (class template)[edit] |
(C++11) | attempts to match a regular expression to an entire character sequence (function template)[edit] |
