Difference between revisions of "cpp/regex/regex search"

#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();
    }
 
   // Example Using C-Strings
   std::cmatch cm;
   const char* cline = "this is a test";
   bool cfound  = std::regex_search(cline, cm, std::regex{R"(test)"});
   if (cfound) {
     cout << "Found: C-String of Length: " << cm.length() << " chars\n";
   }
 
   return;
}

// (1)
  bool regex_search(
    const std::string::iterator   first, //ex: string1.begin()
    const std::string::iterator   last,  //ex: string1.end()
    std::smatch&                  m,
    const std::regex&             e,
    std::regex_constants::match_flag_type flags = std::regex_constants::match_default );
 
  // (2)
  bool regex_search( 
    const CharT*        s,
    std::cmatch&        m,
    const std::regex&   e,
    std::regex_constants::match_flag_type flags = std::regex_constants::match_default );
 
  // (3)
  bool regex_search( 
    const std::string&  s,
    std::smatch&        m,
    const std::regex&   e, 
    std::regex_constants::match_flag_type flags = std::regex_constants::match_default);
 
  // (4)
  bool regex_search( 
    std::string::iterator   first,
    std::string::iterator   last, 
    const std::regex&       e,
    std::regex_constants::match_flag_type flags =  std::regex_constants::match_default 
  );
 
  // (5)
  bool regex_search( 
    const CharT*        s,
    const std::regex&   e,
    std::regex_constants::match_flag_type flags =  std::regex_constants::match_default 
  );
 
  // (6) 
  bool regex_search( 
    const string&     s,
    const std::regex& e,
    std::regex_constants::match_flag_type flags = std::regex_constants::match_default 
  );

// C++11:
  #include <regex>
  std::string s = " ...";
  std::smatch m;
  if (regex_search(s, m, regex{R"(regular_expression)"})) {
    //match
  }
 
  // Perl
  if ($s =~ /regular_expression/) {
    //match
  }