How does one properly use the Unix exec C(++)-command?

If you have a vector of strings then you need to convert it to an array of char* and call execvp

#include <cstdio>#include <string>#include <vector>#include <sys/wait.h>#include <unistd.h>int main() {    using namespace std;    vector<string> args;    args.push_back("Hello");    args.push_back("World");    char **argv = new char*[args.size() + 2];    argv[0] = "echo";    argv[args.size() + 1] = NULL;    for(unsigned int c=0; c<args.size(); c++)        argv[c+1] = (char*)args[c].c_str();    switch (fork()) {    case -1:        perror("fork");        return 1;    case 0:        execvp(argv[0], argv);        // execvp only returns on error        perror("execvp");        return 1;    default:        wait(0);    }    return 0;}

You may be looking for execv() or execvp().

You don't necessarily need google to find this out, you should have the man command available so you can man fork and man exec (or maybe man 2 fork and man 3 exec) to find out about how the parameters to these system and library functions should be formed.

In Debian and Ubuntu, these man pages are in the manpages-dev package which can be installed using synaptic or with:

sudo apt-get install manpages-dev