Getting issue while closing file using android ndk commands?

Question

I am using this code:

try 
{ 
    process = Runtime.getRuntime().exec("su");
    os = new DataOutputStream(process.getOutputStream());
    os.writeBytes("getevent /dev/input/event6 >/sdcard/test.txt \n ");
    os.flush();
} 
catch (Exception e)
{
    LogWrite.d(tag, "error=="+e.toString());
}

i want to stop this process or stop writing to test.txt according to my need. How can i achieve this?

Thanks and Regards