When Runtime.exec() is called with a command that doesn't exist, it doesn't return an error, but it does spew lots of nasty-looking error messages to the output. The following code produces the following output:

import java.io.*;
public class ExecDemo
implements Runnable
{
static Process p;
public static void main(String args[])
{
try {p = Runtime.getRuntime().exec("fredbob");}
catch (IOException e)
{
System.err.println("exec IO Exception: " + e.toString());
return;
}
Thread it = new Thread(new ExecDemo(0));
Thread ot = new Thread(new ExecDemo(1));
Thread et = new Thread(new ExecDemo(2));
//it.start();
ot.start();
et.start();
try {p.waitFor();}
catch (InterruptedException e)
{
System.err.println("Wait interrupted: " + e.toString());
}
System.out.println("Exit value " + p.exitValue());
}
int fd;
public ExecDemo(int fd) {this.fd = fd;}
public void run()
{
OutputStream out;
InputStream in;
if (fd == 0)
{
out = p.getOutputStream();
in = System.in;
}
else if (fd == 1)
{
out = System.out;
in = p.getInputStream();
}
else
{
out = System.err;
in = p.getErrorStream();
}
try
{
int c;
while ((c = in.read()) != -1)
out.write(c);
}
catch (IOException e)
{
System.err.println("IO Error fd " + fd + ": " + e.toString());
}
}
}




Script started on Tue Jul 02 18:43:36 1996
coolant{soule}~/javatest>java ExecDemo
err = 1!
exec of "fredbob" failed with errno 2
SIGABRT 6* abort (generated by abort(3) routine)
    si_signo [6]: SIGABRT 6* abort (generated by abort(3) routine)
    si_errno [0]: Error 0
    si_code [0]: SI_USER [pid: 5806, uid: 33067]
stackbase=EFFFF97C, stackpointer=EFFFF660

Full thread dump:
    "Thread-4" (TID:0xee300920, sys_thread_t:0xef430de0) prio=5
    "Finalizer thread" (TID:0xee3003b0, sys_thread_t:0xef460de0) prio=1
    "Async Garbage Collector" (TID:0xee300368, sys_thread_t:0xef490de0) prio=1
    "Idle thread" (TID:0xee300320, sys_thread_t:0xef4c0de0) prio=0
    "clock handler" (TID:0xee3001f8, sys_thread_t:0xef4f0de0) prio=11
    "main" (TID:0xee3000a0, sys_thread_t:0x812b0) prio=5 *current thread*
java.lang.UNIXProcess.<init>(UNIXProcess.java:121)
java.lang.Runtime.exec(Runtime.java)
java.lang.Runtime.exec(Runtime.java)
ExecDemo.main(ExecDemo.java:8)
Monitor Cache Dump:
Registered Monitor Dump:
    Finalize me queue lock: unowned
    Thread queue lock: unowned
    Class lock: unowned
    Java stack lock: unowned
    Code rewrite lock: unowned
    Heap lock: unowned
    Has finalization queue lock: unowned
    Monitor IO lock: unowned
    Child death monitor: unowned
    Event monitor: unowned
    I/O monitor: unowned
    Alarm monitor: unowned
Waiting to be notified:
"clock handler"
    Sbrk lock: unowned
    Monitor cache lock: unowned
    Monitor registry: monitor owner: "main"
Thread Alarm Q:
IO Error fd 1: java.io.IOException: read error
IO Error fd 2: java.io.IOException: read error
Exit value 6
coolant{soule}~/javatest>exit

script done on Tue Jul 02 18:43:54 1996