std::regex_search
| 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, const std::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( const std::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 expression e and some subsequence in the target character sequence. The detailed match result is stored in m (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 involving m (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()) as n, the following expressions involving m 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 matched e | ||
| m[0].second | the end of the sequence that matched e | ||
| m[0].matched | true | ||
| m[n].first |
| ||
| m[n].second |
| ||
| m[n].matched |
| ||
Contents |
Parameters
| first, last | - | the target character range |
| str | - | the target null-terminated C-style string |
| s | - | the target std::basic_string |
| m | - | the match results |
| e | - | the regular expression |
| flags | - | flags used to determine how the match will be performed |
Return value
Returns true if a match exists, false otherwise.
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.
Example
#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 match for (const auto& line : lines) std::cout << line << ": " << std::boolalpha << std::regex_search(line, color_regex) << '\n'; std::cout << '\n'; // show contents of marked subexpressions within each match std::smatch color_match; for (const auto& 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: 400 Mass: 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 demo std::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: 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
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 2205 | C++11 | n could be zero in the postcondition | can only be positive |
| LWG 2329 | C++11 | overload (5) accepted basic_string rvalues,which could result in dangling iterators |
rejected via deleted overload (7) |
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) |
