How to execute an external tool in unix terminal from java code?

Question

I try to execute a basic command,which is "java -version", in java code. My code works for the shell commands, in example "ls", "echo $PATH" etc. My code :

import java.io.*;

public class cmd {
    public static void main(String[] args) {

        String command = "java -version";
        Process proc = null;
        try {
            proc = Runtime.getRuntime().exec(command);
        } catch (IOException e1) {
            System.out.println( "IOException 1" );
        }

        BufferedInputStream buffer = new BufferedInputStream( proc.getInputStream() );
        BufferedReader commandOutput= new BufferedReader( new InputStreamReader( buffer ) );
        String line = null;
        try {
            while ( ( line = commandOutput.readLine() ) != null ) {
                System.out.println( line );
            }
            commandOutput.close(); 
        } catch ( IOException e) {
            System.out.println( "IOException 2" );
        }
    }
}

The code works without exception or error, but there is not an output.

If String command = "ls", the code could be worked and the output could be seen in the console.

eis · Accepted Answer · 2012-09-09 12:06:20Z

1

Check .getErrorStream() and .getOutputStream() of Process object that you have. You'll likely see an error message there telling you that you need to specify full path to java executable for this to work. However, if the reason is something different, you should see that also when outputting the contents of mentioned streams.

answered Sep 9, 2012 at 12:06

eis

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3 Comments

hcakmak Over a year ago

Specify full path for the tools is useful and working. Thank you.

eis Over a year ago

you should anyway get at least error stream output - if there are any other errors except wrong path, without the error stream you wouldn't have the information what it is about...

hcakmak Over a year ago

I did it ;) better late then never :)

Chris · Accepted Answer · 2012-09-09 12:06:54Z

0

Redirect the command's output to a tempfile like "ls > tempt.txt". That might fix the problem

answered Sep 9, 2012 at 12:06

Chris

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