std::regex_search (3) Linux Manual Page
std::regex_search – std::regex_search
Synopsis
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, (1)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class CharT, class Alloc, class Traits>
bool regex_search(const CharT *str,
std::match_results<const CharT *, Alloc> &m, (2)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
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, (3)(since C++ 11)
Alloc
> &m,
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class BidirIt,
class CharT, class Traits>
bool regex_search(BidirIt first, BidirIt last, (4)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class CharT, class Traits>
bool regex_search(const CharT *str,
const std::basic_regex<CharT, Traits> &e, (5)(since C++ 11)
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
template <class STraits, class SAlloc,
class CharT, class Traits>
bool regex_search(const std::basic_string<CharT, STraits, SAlloc> &s, (6)(since C++ 11)
const std::basic_regex<CharT, Traits> &e,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default);
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, (7)(since C++ 14)
Alloc
> &,
const std::basic_regex<CharT, Traits> &,
std::regex_constants::match_flag_type flags =
std::regex_constants::match_default) = delete;Determines if there is a match between the regular expression e and some subsequence in the target character sequence.
1) Analyzes generic range [first,last). Match results are returned in m.
2) Analyzes a null-terminated string pointed to by str. Match results are returned in m.
3) Analyzes a string s. Match results are returned in m.
4-6) Equivalent to (1-3), just omits the match results.
7) The overload 3 is prohibited from accepting temporary strings, otherwise this function populates match_results m 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.
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.
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
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 <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 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 (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 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();
}
Output:
See also
basic_regex regular expression object
(C++11)
match_results identifies one regular expression match, including all sub-expression matches
(C++11)
regex_match attempts to match a regular expression to an entire character sequence
(C++11)