Run a dos command from a Java class

[Alex Omar Pagan Ortiz]

Hi!

I would like to know a simple routine or the java instructions to just
execute a dos command, like "dir" or "java classname" from a java class.

Regards,

Alex

[Dhimant Patel]

Did you tried Process class in java.lang?
You might need to struggle with it though!

-HTH
DP.

"Alex Omar Pagan Ortiz" <aortiz@dcti.com> wrote:
>
>
>Hi!
>
> I would like to know a simple routine or the java instructions to just
>execute a dos command, like "dir" or "java classname" from a java class.
>
>Regards,
>
>Alex

[Thomas Weinstein]

Hi Alex,

As in the prev. replay mentioned use:
proc = Runtime.getRuntime().exec(String cmdline);

But beware of a nice pitfall which costs me days of debugging.

If you use exec() (at least with Windows NT) you are responsible
to read the stdout and stderr stream of the process you've started. If you
don not so your process will hang and appearantly never terminate. Following
the code I used to solve
this problem. Don't know if this is the most elegant or efficient method
but it works for me.
Just put the proc value you've got from exec() and put it into the following
method:

protected int showOutputAndWaitForProcEnd(Process proc) throws IOException
{
InputStream in = proc.getInputStream();
InputStream err = proc.getErrorStream();
BufferedReader readIn = new BufferedReader(
new InputStreamReader(in));
BufferedReader readErr = new BufferedReader(
new InputStreamReader(err));
int b;
int exit = -1;

boolean bReady = false;

while (!bReady)
{
try
{
exit = proc.exitValue();
bReady = true;
}
catch (IllegalThreadStateException isex)
{
}
suckStreams(readIn,readErr);
}

readIn.close();
readErr.close();

return exit;
}

protected void suckStreams(BufferedReader readIn, BufferedReader readErr)
{
try
{
while (readIn.ready() || readErr.ready())
{
if (readIn.ready()) System.out.println(readIn.readLine());
if (readErr.ready())
System.err.println(readErr.readLine());
}
}
catch (IOException ex)
{
System.err.println("suckStreams: " + ex);
}
}

"Alex Omar Pagan Ortiz" <aortiz@dcti.com> wrote:
>
>
>Hi!
>
> I would like to know a simple routine or the java instructions to just
>execute a dos command, like "dir" or "java classname" from a java class.
>
>Regards,
>
>Alex