Separating a string in C++

Question

I am trying to separate a string into multiple strings, to make a customized terminal. So far I have been separating control signals using strtok, however I do not understand how to separate specific instances of a character. For example:

string input = "false || echo \"hello world\" | grep hello";

When trying to strtok this input and trying to separate using | the output would be:

false , echo "hello world" , grep hello

Instead, I would like the output to be:

false || echo "hello world" , grep hello

How can I have strtok treat | and || differently rather than having it saying they are the same?

Answer 1

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
using namespace std;

vector<string> split(string sentence,char delim)
{
    string tempSentence = "";
    tempSentence += delim;
    tempSentence += sentence;
    tempSentence += delim;

     string token;
     vector<string> tokens;
    for (int i=1;i<tempSentence.length()-1;++i)
    {
        if (tempSentence[i] == delim && tempSentence[i-1] != delim && tempSentence[i+1] != delim)
        {
            if (token.length()) tokens.push_back(token);
            token.clear();
        }
        else
        {
            token += tempSentence[i];
        }
    }
    if (token.length()) tokens.push_back(token);

    return tokens;
}

int main() {
    string sentence = "false || echo \"hello world\" | grep hello";
    char delim='|';

    vector<string> tokens = split(sentence,delim);


    for_each(tokens.begin(), tokens.end(), [&](string t) {   
        cout << t << endl;
    });

}

ugly and long! but works!

Answer 2

strtok() is going to scan character by character, without regard to characters before and after what it is looking for. If you want a smarter scan, you'll need to implement the additional check yourself.

Since strtok just returns a location within the string where a token is found, you'd have to manually check the first character of the token being returned to see if it is also a '|', and then act accordingly.

A better solution would be to look into the use of a regular expression here. It sounds like the symbol you want to split on is not just a |, but rather a | surrounded by spaces -- ie, you are actually searching and splitting on a three character symbol (space - pipe - space)