how can I get the return value of a program executed by exec? [duplicate]

Answer 1

Have the parent process wait for the child to exit:

pid_t pid = fork();
if (pid == -1) {
  // error, no child created
}
else if (pid == 0) {
  // child
}
else {
  // parent
  int status;
  if (waitpid(pid, &status, 0) == -1) {
    // handle error
  }
  else {
    // child exit code in status
    // use WIFEXITED, WEXITSTATUS, etc. on status
  }
}