I have a program where I was able to successfully execute cmd commands from my code, but I want to be able to get the output from the cmd command. How can I do that?
So far my code is:
Second.java:
public class Second {
public static void main(String[] args) {
System.out.println("Hello world from Second.java");
}
}
and Main.java
public class Main {
public static void main(String[] args) {
String filename = args[1].substring(0, args[1].length() - 5);
String cmd1 = "javac " + args[1];
String cmd2 = "java " + filename;
Runtime r = Runtime.getRuntime();
Process p = r.exec(cmd1); // i can verify this by being able to see Second.class and running it successfully
p = r.exec(cmd2); // i need to see this output to see if
System.out.println("Done");
}
}
I can check the first command is working successfully by checking for Second.class, but what if this class generated some error, how will I be able to see that error?
You need to the OutputStream (InputStream) of your Process (and you should use a ProcessBuilder)... like so
public static void main(String[] args) {
String filename = args[1].substring(0, args[1].length() - 5);
String cmd1 = "javac " + args[1];
String cmd2 = "java " + filename;
try {
// Use a ProcessBuilder
ProcessBuilder pb = new ProcessBuilder(cmd1);
Process p = pb.start();
InputStream is = p.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
int r = p.waitFor(); // Let the process finish.
if (r == 0) { // No error
// run cmd2.
}
} catch (Exception e) {
e.printStackTrace();
}
}