child_pid          49 popen.cpp        pid_t child_pid;
child_pid          99 popen.cpp        child_pid = fork();
child_pid         100 popen.cpp        if (child_pid == 0) {
child_pid         127 popen.cpp        if (child_pid < 0) {
child_pid         139 popen.cpp          _dmtcpPopenPidMap[fp] = child_pid;