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How do I tokenize a string in C++?
Hello I was wondering how I would tokenize a std string with strtok
string line = "hello, world, bye"; char * pch = strtok(line.c_str(),","); I get the following error
error: invalid conversion from ‘const char*’ to ‘char*’ error: initializing argument 1 of ‘char* strtok(char*, const char*)’ I'm looking for a quick and easy approach to this as I don't think it requires much time
I always use getline for such tasks.
istringstream is(line); string part; while (getline(is, part, ',')) cout << part << endl; 
std::string::size_type pos = line.find_first_of(','); std::string token = line.substr(0, pos); to find the next token, repeat find_first_of but start at pos + 1.
You can use strtok by doing &*line.begin() to get a non-const pointer to the char buffer. I usually prefer to use boost::algorithm::split though in C++.
std::string into an undefined state. You are not supposed to modify a std::string using C string functions.
const could change other copies of the string. It might (or might not) be possible to demonstrate that what you're doing is well-defined for any conformant implementation, but even if you can, I wouldn't like to test the edge cases of conformance like that.strtok writes to the buffer. Are there any implementations that actually do CoW?strtok is a rather quirky, evil function that modifies its argument. This means that you can't use it directly on the contents of a std::string, since there's no way to get a pointer to a mutable, zero-terminated character array from that class.
You could work on a copy of the string's data:
std::vector<char> buffer(line.c_str(), line.c_str()+line.size()+1); char * pch = strtok(&buffer[0], ","); or, for more of a C++ idiom, you could use a string-stream:
std::stringstream ss(line); std::string token; std::readline(ss, token, ','); or find the comma more directly:
std::string token(line, 0, line.find(',')); 
