CODEWITHSUNDEEP
javajavafxjavafx-2
user3649361
user3649361

Reputation: 954

Getting Output from the java process

I am building a javaFx application I am running a command using java process builder class.

ProcessBuilder builder = new ProcessBuilder(runCommand);
builder.redirectErrorStream(true);
Process process = builder.start();
try {
    process.waitFor();
} catch (InterruptedException e) {
    e.printStackTrace();
}

I am trying to get the output from the process I have tried two different ways but I am not able to get it.

InputStream stdout = process.getInputStream();
InputStream stderr = process.getErrorStream ();
BufferedReader reader = new BufferedReader (new InputStreamReader(stdout));
String line1=null;
while ((line1 = reader.readLine()) != null) {
    System.out.println(line1);
}
BufferedReader errorred = new BufferedReader (new InputStreamReader(stderr));
while ((line1 = errorred.readLine()) != null) {
    System.out.println(line1);
}

I tried also this:

ProcessBuilder builder = new ProcessBuilder(runCommand);
//String outputLogs = new VerboseProcess(new ProcessBuilder(""));
builder.redirectErrorStream(true);
builder.redirectOutput(Redirect.INHERIT);
builder.redirectError(Redirect.INHERIT);
builder.redirectInput(Redirect.INHERIT);
Process process = builder.start();
try {
    process.waitFor();
} catch (InterruptedException e) {
    e.printStackTrace();
}

Upvotes: 1

Views: 2649

Answers (1)

SubOptimal
SubOptimal

Reputation: 22993

I believe the error is somewhere else. Following snippet is based on your posted code

ProcessBuilder builder = new ProcessBuilder("java.exe", "-version");
builder.redirectErrorStream(true);
Process process = builder.start();
process.waitFor();
int exitValue = process.exitValue();
System.out.println("exitValue = " + exitValue);

InputStream stdout = process.getInputStream();
InputStream stderr = process.getErrorStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(stdout));
String line1 = null;
while ((line1 = reader.readLine()) != null) {
    System.out.println(line1);
}
BufferedReader errorred = new BufferedReader(new InputStreamReader(stderr));
while ((line1 = errorred.readLine()) != null) {
    System.out.println(line1);
}

and produces the following output on the console

exitValue = 0
java version "1.8.0_74"
Java(TM) SE Runtime Environment (build 1.8.0_74-b02)
Java HotSpot(TM) 64-Bit Server VM (build 25.74-b02, mixed mode)

If the command specified in new ProcessBuilder(command...) does not exists or is not in the PATH an IOException is thrown

Cannot run program "...": CreateProcess error=2, The system \
    cannot find the file specified

If you don't get any output. Following could be the reason:

  • the process has not printed anything to stdout/stderr
  • your runcommand start the process in a background process, e.g. on Linux/OSX command & or on Windows start command.exe

Upvotes: 1

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