Writing to InputStream of a Java Process
This is an example which maybe can helps someone
import java.io.IOException;
import java.io.File;
import java.io.OutputStream;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Scanner;
public class Main {
public static void main(String[] args) throws IOException {
String[] commands = {"C:/windows/system32/cmd.exe"};
ProcessBuilder builder = new ProcessBuilder(commands);
builder.directory(new File("C:/windows/system32"));
Process process = builder.start();
OutputStream stdin = process.getOutputStream();
InputStream stdout = process.getInputStream();
InputStream stderr = process.getErrorStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(stdout));
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(stdin));
BufferedReader error = new BufferedReader(new InputStreamReader(stderr));
new Thread(() -> {
String read;
try {
while ((read = reader.readLine()) != null) {
System.out.println(read);
}
} catch (IOException e) {
e.printStackTrace();
}
}).start();
new Thread(() -> {
String read;
try {
while ((read = error.readLine()) != null) {
System.out.println(read);
}
} catch (IOException e) {
e.printStackTrace();
}
}).start();
new Thread(() -> {
while (true) {
try {
Scanner scanner = new Scanner(System.in);
writer.write(scanner.nextLine());
writer.newLine();
writer.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
}
The Process
OutputStream
(our point of view) is the STDIN from the process point of view
OutputStream stdin = process.getOutputStream(); // write to this
So what you have should be correct.
My driver (apply your own best practices with try-with-resources statements)
public class ProcessWriter {
public static void main(String[] args) throws Exception {
ProcessBuilder builder = new ProcessBuilder("java", "Test");
builder.directory(new File("C:\\Users\\sotirios.delimanolis\\Downloads"));
Process process = builder.start();
OutputStream stdin = process.getOutputStream(); // <- Eh?
InputStream stdout = process.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(stdout));
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(stdin));
writer.write("Sup buddy");
writer.flush();
writer.close();
Scanner scanner = new Scanner(stdout);
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
}
}
}
My application
public class Test {
public static void main(String[] args) throws Exception {
Scanner console = new Scanner(System.in);
System.out.println("heello World");
while(console.hasNextLine()) {
System.out.println(console.nextLine());
}
}
}
Running the driver prints
heello World
Sup buddy
For some reason I need the close()
. The flush()
alone won't do it.
Edit It also works if instead of the close()
you provide a \n
.
So with
writer.write("Sup buddy");
writer.write("\n");
writer.write("this is more\n");
writer.flush();
the driver prints
heello World
Sup buddy
this is more