std::regex_search
From cppreference.com
| Defined in header <regex>
|
||
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 );
|
(1) | (since C++11) |
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 );
|
(2) | (since C++11) |
template< class CharT, class Alloc, class Traits >
bool regex_search( 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 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 );
|
(4) | (since C++11) |
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 );
|
(5) | (since C++11) |
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 );
|
(6) | (since C++11) |
template< class STraits, class SAlloc, class Alloc,
class CharT, class Traits >
bool regex_search
( const std::basic_string<CharT, STraits, SAlloc>&&,
std::match_results
<typename std::basic_string<CharT, STraits, SAlloc>::const_iterator,
Alloc>&,
const std::basic_regex<CharT, Traits>&,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default ) = delete;
|
(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).
1,2) The target character sequence is represented by the range
[first, last).
|
If |
(until C++23) |
|
If |
(since C++23) |
3,4) The target character sequence is represented by the range
[str, str + std::char_traits<CharT>::length(str)).5,6) The target character sequence is represented by the string
s.7) The target character sequence cannot be represented by a std::string rvalue.
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
|
| ||
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
Run this code
#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) |
