(This is a question my coworker posted elsewhere, but I thought I'd post it here to see if I could hit a different audience.)
Hello all, I'm testing the possibility of writing a small java application the will use Psexec to kick off remote jobs. In the course of testing binding the stdin and stdout of a java program to psexec I came across an odd bug.
My test program is a basic echo program. It starts a thread to read from stdin and then pipes the read output directly back to stdout. When run on the local machine, not from psexec, it works beautifully. Exactly as it should.
However, when I call it from PsExec the first time the input is piped directly into stdout it is lost. What makes the bug really bizzare is that it is only the first time the input is piped directly into stdout that it is lost. If the input String is appended to another string it works fine. Either a String literal or a String variable. However, if the input String is sent directly to stdout it doesn't go through. The second time it is sent to stdout it goes through fine - and everytime there after.
I'm at a complete loss as to what's going on here. I've tried to test for every possible bug I can think of. I'm out of ideas. Did I miss one or is this just something inside psexec?
Here is the code in question, it's in three classes (one of which implements an interface which is a single function interace).
The Main class:
public class Main {
public static void main(String[] args) {
System.out.println("Starting up.");
CReader input = new CReader(new BufferedReader(
new InputStreamReader(System.in)));
CEcho echo = new CEcho();
input.addInputStreamListener(echo);
input.start();
System.out.println("Successfully started up. Awaiting input.");
}
}
The CReader class which is the thread that reads from stdin:
public class CReader extends Thread {
private ArrayList<InputStreamListener> listeners =
new ArrayList<InputStreamListener>();
private boolean exit = false;
private Reader in;
public CReader(Reader in) {
this.in = in;
}
public void addInputStreamListener(InputStreamListener listener) {
listeners.add(listener);
}
public void fireInputRecieved(String input) {
if(input.equals("quit"))
exit = true;
System.out.println("Input string has made it to fireInputRecieved: "
+ input);
for(int index = 0; index < listeners.size(); index++)
listeners.get(index).inputRecieved(input);
}
@Override
public void run() {
StringBuilder sb = new StringBuilder();
int current = 0, last = 0;
while (!exit) {
try {
current = in.read();
}
catch (IOException e) {
System.out.println("Encountered IOException.");
}
if (current == -1) {
break;
}
else if (current == (int) '\r') {
if(sb.toString().length() == 0) {
// Extra \r, don't return empty string.
continue;
}
fireInputRecieved(new String(sb.toString()));
sb = new StringBuilder();
}
else if(current == (int) '\n') {
if(sb.toString().length() == 0) {
// Extra \n, don't return empty string.
continue;
}
fireInputRecieved(new String(sb.toString()));
sb = new StringBuilder();
}
else {
System.out.println("Recieved character: " + (char)current);
sb.append((char) current);
last = current;
}
}
}
}
The CEcho class, which is the class that pipes it back to stdout:
public class CEcho implements InputStreamListener {
public void inputRecieved(String input) {
System.out.println("\n\nSTART INPUT RECIEVED");
System.out.println("The input that has been recieved is: "+input);
System.out.println("It is a String, that has been copied from a " +
"StringBuilder's toString().");
System.out.println("Outputting it cleanly to standard out: ");
System.out.println(input);
System.out.println("Outputting it cleanly to standard out again: ");
System.out.println(input);
System.out.println("Finished example outputs of input: "+input);
System.out.println("END INPUT RECIEVED\n\n");
}
}
And finally, here is the program output:
>psexec \\remotecomputer "C:\Program Files\Java\jre1.6.0_05\bin\java.exe" -jar "C:\Documents and Settings\testProram.jar" PsExec v1.96 - Execute processes remotely Copyright (C) 2001-2009 Mark Russinovich Sysinternals - www.sysinternals.com Starting up. Successfully started up. Awaiting input. Test Recieved character: T Recieved character: e Recieved character: s Recieved character: t Input string has made it to fireInputRecieved: Test START INPUT RECIEVED The input that has been recieved is: Test It is a String, that has been copied from a StringBuilder's toString(). Outputting it cleanly to standard out: Outputting it cleanly to standard out again: Test Finished example outputs of input: Test END INPUT RECIEVED