How to extract a specific number from a string that can have almost any shape, I explain:
My string can be: cualquiercosa+CH+number+cualquiercosa
that is: TEST-13?:41CH12f:A1345
I just need to extract the number that follows CH and convert it to int .
The format of the string seems quite closed despite the randomness of it, the following expressions can help you to extract the number:
.+CH(\d+).+ . \w+-\d+\?:\d+CH(\d+)f:.+ . Depending on how restrictive you want to be, you should use one or the other.
The header <regex> added to C ++ in the C ++ 11 standard automates the process of using expressions Regular:
std::regex expresion(R"(\w+-\d+\?:\d+CH(\d+)f:.+)");
std::cmatch coincidencias;
std::regex_search(texto, coincidencias, expresion);
After the call to std::regex_search the object std::cmatch (which is a version of std::match_result for character strings char ) will contain the captured text of the regular expression, the first being capture in position 1.
You can use the std::atoi function in the header <cstdlib> :
int numero = std::atoi(coincidencias[1].str().c_str());
The std::atoi function expects to receive a pointer to a string of characters. The bracket operator ( [] ) of the object std::match_result returns an object sub_match that has a function to convert to std::string .
But I prefer the option to use a text stream :
std::stringstream stream(coincidencias[1].str());
int numero = 0;
stream >> numero;
[Here] you can see the code working:
int main()
{
constexpr char text[]{"TEST-13?:41CH12f:A1345"};
std::regex expresion(R"(\w+-\d+\?:\d+CH(\d+)f:.+)");
std::cmatch coincidencias;
std::regex_search(text, coincidencias, expresion);
std::stringstream stream(coincidencias[1].str());
int numero = 0;
stream >> numero;
std::cout << numero;
return 0;
}