About Runtime

[WhiteSox]

old question, new variation.

we all know the following piece does work well:

String cmd = "ls";
Process proc = Runtime.getRuntime().exec(cmd);

here, the external command is simple enough.

now, i wanna play with pipe. for example, i wanna execute
"ls -l | grep -i abc" with Runtime (i think it's the only way). i've studied the article at

http://www.javaworld.com/jw-12-2000/jw-1229-traps.html,

but their samples don't work for me, neither in windows nor in linux.

any hints are highly appreciated.

 

[Vepo]

Hi WhiteSox,

I was also unable to get those examples work, but I checket at

http://www.jguru.com/faq/printablefaq.jsp?topic=Linux

one similar example and it seemed to work.

So try this:

_____________________________________________

String[] cmd = { "sh", "-c", "ls -al | grep java" };
try
{

Process p = Runtime.getRuntime().exec(cmd);

BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));

String str = null;
while((str = br.readLine()) != null)
{
System.out.println(str);
}
}
catch(IOException ioe)
{
System.out.println(ioe.toString());
}

Well, this works at Linux, for some reason you have to call a new shell... I don't have much experience of Runtime, but I hope this helped you.

 

[WhiteSox]

Vepo,

Your code does really work for me, though it doesn't look good. i know it's J's fault, not yours. Thanks a lot for your hint.

I've figured out what's preventing me from running the samples @ at

http://www.javaworld.com/jw-12-2000/jw-1229-traps.html.

add "proc.waitFor()" before retrieving error message as the following:

FileOutputStream fos = new FileOutputStream(args[0]);
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("ls -l"

proc.waitFor();

// any error message?
StreamGobbler errorGobbler = new
StreamGobbler(proc.getErrorStream
(), "ERROR"

Thanks again,

WS