use c++ to call external programme and terminate conditionally

[cannon_1]

Currently, I have a c++ program to call an external program, wait for it to finish, and return the string that was supposed to print on the screen by the external program;

string result_now=exec("./CCLS_to_akmaxsat "+softer_filename);

std::string exec(std::string command) {
    //cout << "\n\nEvaluating command: " << command << "\n\n" << endl;
    const char* cmd = command.c_str();
    FILE* pipe = popen(cmd, "r");
    if (!pipe) return "ERROR";
    char buffer[256];
    std::string result = "";
    while(!feof(pipe)) {
        if(fgets(buffer, 256, pipe) != NULL)
            result += buffer;
    }
    pclose(pipe);
    return result;
}

And here is the output:

c This is the CCLS_to_akmaxsat solver, Version: MAXSAT EVALUATION 2014 (2014.03.28)
c Many thanks to the akmaxsat team!
c start CCLS
c stop CCLS
c start akmaxsat
c initialized bestCost to 924115047
o 924115047
c first lower bound: 850209662
c 3406 branches 129 propagates
c total generalized unit propagation = 6941, success = 49.07%
s OPTIMUM FOUND
c Optimal Solution = 924115047
v -60 -58 -56 -54 52 50 48 46 44 42 40 38 36 34 32 30 28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 21 23 -25 -27 -29 -31 -33 -35 -37 -39 -41 -43 -45 -47 -49 -51 -53 -55 -57 59 19 17 15 13 11 9 7 5 3 1
c stop akmaxsat

However, if I see that the lower bound is larger than some value. I no longer want to spend time waiting to program to finish, rather I would terminate the program and provide some information back to my main c++ solver. How do I achieve this? Or if you have some very related tutorials, please don't hesitate to tell me. Thank you.

[tinstaafl]

Have you tried testing result inside the while loop and breaking if the condition is met? You may have to send an escape sequence to other program to tell it to quit as well. That of course will depend on the program.