Re: Capturing stdout from runtime exec

From:
 jean.francois.henrard@gmail.com
Newsgroups:
comp.lang.java.help
Date:
Tue, 03 Jul 2007 05:05:15 -0700
Message-ID:
<1183464315.649598.92720@w5g2000hsg.googlegroups.com>
On 15 mai, 21:43, Lax <lax_re...@hotmail.com> wrote:

Hello all,
I'm trying to run an Unix cmd from runtime exec and trying to capture
the cmd's output.
e.g., /usr/bin/echo Foo > Foo.txt
I'm expecting my Java program to echo Foo and redirect it to Foo.txt
file.
However, on running the program, I get " Foo > Foo.txt".
Looks like the greater than (>) operator is not being intepreted
properly.
Could anyone give me some pointers on this, please?

-------------------------------------------
import java.io.* ;
import java.lang.* ;

public class RunUnixCommand {
        public static void main(String args[]) {
                String s = null;

                String[] cmd = new String[4] ;
                cmd[0] = "/usr/bin/echo" ;
                cmd[1] = "Foo" ;
                cmd[2] = ">" ;
                cmd[3] = "Foo.txt" ;
                System.out.println("Run CMD: " + cmd[0] + " " +
cmd[1] + " " + cmd[2] + " " + cmd[3] ) ;

                try {
                        Process p = Runtime.getRuntime().exec(cmd);
                        int i = p.waitFor();
                        if (i == 0){

                                // STDOUT
                                BufferedReader input = new
BufferedReader(new InputStreamReader(p.getInputStream()));
                                while ((s = input.readLine()) != null)
{
                                        System.out.println(s);
                                }
                        } else {

                                // STDERR
                                BufferedReader stderr = new
BufferedReader(new InputStreamReader(p.getErrorStream()));
                                while ((s = stderr.readLine()) !=
null) {
                                        System.out.println(s);
                                }
                        }
                } catch (Exception e) {
                        System.out.println(e) ;
                }
        }

}

Thanks for your time,
Lax


still waiting for help ?

You must do the redirection yourself.
It is not a shell but a process that will be launched by your java
app.

And more, the process has got a buffer for outpouts.
If the buffer becomes full, the process will be blocked if it wants to
write something.
You have to start a thread to read the outputs to avoid that.

Bye.

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