Hello,
In my program, I need to run a external command in a Ubuntu environment (ntpdate) using java. Currently my code looks like this:
Runtime rt = Runtime.getRuntime();
byte[] readBuffer = new byte[131072];
// Exec a process to do the query
Process p = null;
try {
p = rt.exec("ntpdate -q " + ip);
} catch (Exception ex) {
ex.printStackTrace();
}
if(p!= null){
try {
Thread.sleep(1000);
} catch (Exception e) {
}
// Read the input stream, copy it to the file
InputStream in = p.getInputStream();
try {
int count = 0, rc;
while ((rc = in.read(readBuffer, count, readBuffer.length - count)) != -1) {
count += rc;
if (count >= readBuffer.length) {
p.destroy();
break;
}
}
p.destroy();
result = processOutput(readBuffer, count);
} catch (IOException ex) {
ex.printStackTrace();
}
p.destroy();
This code need to be ran simultaneously on multiple threads in order to maximize performance (I need to test a list of 1.000.000 addresses using ntpdate). However, it runs very slowly, barely consuming machine processing. What am I doing wrong? How could I make this more efficient?
The same problem arises when trying to execute "dig" using .exec(), so I doubt it is because of the specific program being called. Is there some restriction in using Runtime.exec() in a multi Threaded environment?