Process.getInputStream and Process.getOutputStream

Question

Hi,
I'm using JDK 1.4.0 for Linux. I need to execute an external program. Then get the output from the program and provide input to the program. Below is the code I wrote. This code works fine if I execute "passwd" to change password. But when I execute "scp2" or "ftp", it just blocks. I don't know why. I've spent days to figure out this problem. But I still haven't got a clue. I'd really appriciate help from you.
Thanks.
public class TestProcess {
public static void main(String[] args) {
System.
try {
Process p = Runtime.getRuntime().exec("scp2 /home/fms/txt root@localhost:./txt");
//Process p = Runtime.getRuntime().exec("passwd");
BufferedReader ireader = new BufferedReader(new InputStreamReader(p.getInputStream()));
BufferedReader ereader = new BufferedReader(new InputStreamReader(p.getErrorStream()));
PrintWriter writer = new PrintWriter(p.getOutputStream(), false);
StreamReader inputReader = new StreamReader("Input", ireader);
inputReader.start();
StreamReader errorReader = new StreamReader("Error", ereader);
errorReader.start();
Thread.currentThread().sleep(20000);
String password = "password\r\n";
for (int i=0; i<password.length(); i++) {
writer.write(password.charAt(i));
writer.flush();
Thread.currentThread().sleep(1);
System.out.println("Password entered.");
Thread.currentThread().sleep(20000);
for (int i=0; i<password.length(); i++) {
writer.write(password.charAt(i));
writer.flush();
Thread.currentThread().sleep(1);
System.out.println("Password entered.");
p.waitFor();
ereader.close();
ireader.close();
writer.close();
System.out.println(p.exitValue());
} catch (Exception e) {
System.out.println(e.getMessage());
class StreamReader extends Thread {
Reader input;
int c;
char[] chars = new char[1000];
String line;
String threadName;
public StreamReader(String threadName, Reader input) {
this.input = input;
this.threadName = threadName;
public void run() {
try {
while ((c = input.read(chars)) != -1) {
line = new String(chars, 0, c);
System.out.print(threadName + " " + line);
} catch (Exception e) {
System.out.println(e.getMessage());
System.out.println(threadName + " quit.");

Answer 1

why are u using BufferedReader? That's useless because read(char[]) isn't overwritten by BufferedReader.
did u read the description of Reader.read(char[])??
try to use this class...
public class TestProcess
private PrintWriter writer;
private Process proc;
private StreamReader inputReader;
private StreamReader errorReader;
public TestProcess(String strFilename)
throws Exception
proc = Runtime.getRuntime().exec(strFilename);
writer = new PrintWriter(proc.getOutputStream(), false);
inputReader = new StreamReader("Input", new InputStreamReader(proc.getInputStream()));
errorReader = new StreamReader("Error", new InputStreamReader(proc.getErrorStream()));
new Thread(inputReader).start());
new Thread(errorReader.start());
public void write(char c)
writer.write(c);
writer.flush();
public void waitFor()
p.waitFor();
public int exitValue()
return p.exitValue();
public void close()
proc.destroy();
writer.close();
class StreamReader
implements Runnable
private Reader input;
private String threadName;
public StreamReader(String threadName, Reader input)
this.input = input;
this.threadName = threadName;
public void run()
try
while ((c = input.read()) != -1)
System.out.print(c);
catch (Exception e)
System.out.println(e.getMessage());
System.out.println(threadName + " quit.");
}...didn''t test it. good luck ;)
if there are still problems, please tell me where it hangs.
~elchaschab