Difference between revisions of "cpp/regex/regex search"
(how to find all occurrences appears to be a frequently asked question. +note) |
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| Line 128: | Line 128: | ||
In order to examine all matches within the target sequence, {{tt|std::regex_search}} may be called in a loop, restarting each time from {{tt|m[0].second}} of the previous call. {{lc|std::regex_iterator}} offers an easy interface to this iteration. | In order to examine all matches within the target sequence, {{tt|std::regex_search}} may be called in a loop, restarting each time from {{tt|m[0].second}} of the previous call. {{lc|std::regex_iterator}} offers an easy interface to this iteration. | ||
| − | === | + | ===Examples=== |
{{example | {{example | ||
| code= | | code= | ||
| Line 173: | Line 173: | ||
3: ff | 3: ff | ||
matches for 'all of my base are belong to you' | matches for 'all of my base are belong to you' | ||
| + | }} | ||
| + | |||
| + | {{example | ||
| + | | code= | ||
| + | #include <iostream> | ||
| + | #include <regex> | ||
| + | #include <string> | ||
| + | // Parse some log | ||
| + | int main () | ||
| + | { | ||
| + | using namespace std; | ||
| + | string log(R"( | ||
| + | Speed: 366 | ||
| + | Mass: 35 | ||
| + | Speed: 378 | ||
| + | Mass: 32 | ||
| + | Speed: 400 | ||
| + | Mass: 30)"); | ||
| + | regex r(R"(Speed:\t\d*)"); | ||
| + | smatch sm; | ||
| + | while(regex_search(log,sm,r)) | ||
| + | { | ||
| + | cout << sm.str() << endl; | ||
| + | log = sm.suffix().str(); | ||
| + | } | ||
| + | return 0; | ||
| + | } | ||
| + | | output= | ||
| + | Speed: 366 | ||
| + | Speed: 378 | ||
| + | Speed: 400 | ||
}} | }} | ||
Revision as of 14:09, 15 June 2016
| 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++14) |
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.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 |
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 | ||
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.
Examples
#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})"); for (const auto &line : lines) { std::cout << line << ": " << std::regex_search(line, color_regex) << '\n'; } std::smatch color_match; for (const auto &line : lines) { std::regex_search(line, color_match, color_regex); std::cout << "matches for '" << line << "'\n"; for (size_t i = 0; i < color_match.size(); ++i) std::cout << i << ": " << color_match[i] << '\n'; } }
Output:
Roses are #ff0000: 1 violets are #0000ff: 1 all of my base are belong to you: 0 matches for 'Roses are #ff0000' 0: #ff0000 1: ff 2: 00 3: 00 matches for 'violets are #0000ff' 0: #0000ff 1: 00 2: 00 3: ff matches for 'all of my base are belong to you'
#include <iostream> #include <regex> #include <string> // Parse some log int main () { using namespace std; string log(R"( Speed: 366 Mass: 35 Speed: 378 Mass: 32 Speed: 400 Mass: 30)"); regex r(R"(Speed:\t\d*)"); smatch sm; while(regex_search(log,sm,r)) { cout << sm.str() << endl; log = sm.suffix().str(); } return 0; }
Output:
Speed: 366 Speed: 378 Speed: 400
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) |
