Use exec/fork to run external process

I am using C++ and trying to run a shell command in an external process. Here is the code I have so far:

pid_t pid;
pid = fork();
if(pid == 0){ 
    execv(args[0],args);
} else {
    wait();
}

My first problem is that I 开发者_如何学JAVAneed to get the output from the shell command passed to exec and I do not know how to get that. After running the code above the main program also duplicates itself and I am not sure why.

args[0] is presumably the name of the running program, so it will fork and then exec itself.

In order to collect output, you will need to arrange to explicitly pass it. The Unix pipe() call is frequently used for this.