wait_pid          153 popen.cpp        pid_t wait_pid;
wait_pid          169 popen.cpp          wait_pid = waitpid(pid, &wstatus, 0);
wait_pid          170 popen.cpp        } while (wait_pid == -1 && errno == EINTR);
wait_pid          171 popen.cpp        if (wait_pid == -1) {