do_read            52 popen.cpp        int do_read = 0;
do_read            58 popen.cpp              do_read = 1;
do_read            72 popen.cpp        if ((do_read ^ do_write) == 0) {
do_read            87 popen.cpp          if (do_read) {
do_read           101 popen.cpp          int child_std_fd = do_read ? STDOUT_FILENO : STDIN_FILENO;