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Using strtok with a std::string

Asked 2008-11-14T06:14:46.540
63

I have a string that I would like to tokenize. But the C strtok() function requires my string to be a char*. How can I do this simply?

I tried:

token = strtok(str.c_str(), " "); 

which fails because it turns it into a const char*, not a char*

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1 Answer

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  1. If boost is available on your system (I think it's standard on most Linux distros these days), it has a Tokenizer class you can use.

  2. If not, then a quick Google turns up a hand-rolled tokenizer for std::string that you can probably just copy and paste. It's very short.

  3. And, if you don't like either of those, then here's a split() function I wrote to make my life easier. It'll break a string into pieces using any of the chars in "delim" as separators. Pieces are appended to the "parts" vector:

    void split(const string& str, const string& delim, vector<string>& parts) {
      size_t start, end = 0;
      while (end < str.size()) {
        start = end;
        while (start < str.size() && (delim.find(str[start]) != string::npos)) {
          start++;  // skip initial whitespace
        }
        end = start;
        while (end < str.size() && (delim.find(str[end]) == string::npos)) {
          end++; // skip to end of word
        }
        if (end-start != 0) {  // just ignore zero-length strings.
          parts.push_back(string(str, start, end-start));
        }
      }
    }
    
answered 2008-11-14T06:28:00.400

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