modern replacement for strtok

split.h

#include <string>
#include <vector>

// If you are using strtok, or a variant like strtok_r or strtok_s, in your
// C++ code, you may be interested in this instead.
//
// This header contains a function called `split`, that takes a string, and
// an array of delimiting characters, and breaks the string on the delimiters,
// in a way similar to strtok, and returns a vector of strings representing
// the tokens.
//
// In brief, split is like strtok but is thread-safe and is called only once
// and returns a vector of tokens.
//
// Example:
//     // tokenizing
//     std::vector<std::string> tokens = split("ab c  d efg h ", " ");
//     // using the tokens
//     for (size_t i = 0; i < tokens.size(); ++i)
//         std::cout << tokens[i] << "\n";
//   Output:
//     ab
//     c
//     d
//     efg
//     h
// License: CC0 (Public Domain)

// splits the given string on every given delimiter and returns a vector
// of strings.
std::vector<std::string>
split(
        const std::string& input,
        const std::string& delims)
{
    std::vector<std::string> ret;
    for (size_t start = 0, pos; ; start = pos + 1) {
        pos = input.find_first_of(delims, start);
        std::string token = input.substr(start, pos - start);
        if (token.length() > 0)  // ignore empty tokens
            ret.push_back(token);
        if (pos == std::string::npos) break;
    }
    return ret;
}

test.cpp

#include <iostream>
#include "split.hpp" // includes string and vector

// This file is used mainly for testing split() during it developing;
// you don't need to get it.

using std::string;
using std::vector;
using std::cout;

#define test_split(s, d) do { \
    vector<string> v = split(s, d); \
    cout << "\n\"" s << "\" separated by \"" d "\" " \
         << "has " << v.size() << " tokens\n"; \
    for (size_t i = 0, len = v.size(); i < len; ++i) \
        cout << " -> " << v[i] << "\n"; \
} while (0)

int main()
{
    if (0) { // example
        std::vector<std::string> tokens = split("ab c  d efg h ", " ");
        for (size_t i = 0; i < tokens.size(); ++i)
            std::cout << tokens[i] << "\n";
    }
    if (1) { // testing split
        test_split("Hello", "l");
        test_split("Helalo", "l");
        test_split("Helloo", "l");
        test_split("Helaloo", "l");
        test_split("Hellool", "l");
        test_split("Helalool", "l");
        test_split("lHellool", "l");
        test_split("lHelalool", "l");
        test_split("lHelloo", "l");
        test_split("lHelaloo", "l");
    }
}