child_fd           47 popen.cpp        int parent_fd, child_fd;
child_fd           89 popen.cpp            child_fd = pipe_fds[1];
child_fd           93 popen.cpp            child_fd = pipe_fds[0];
child_fd          103 popen.cpp          if (child_fd != child_std_fd) {
child_fd          104 popen.cpp            dup2(child_fd, child_std_fd);
child_fd          105 popen.cpp            close(child_fd);
child_fd          126 popen.cpp        close(child_fd);