How to call Perl in Java?

Use Runtime.exec to execute the Perl interpreter

http://technojeeves.com/joomla/index.php/free/52-runtimeexec

Can you please send me a simple example? such as a perl code that prints "hello world" which is called in a Java code.

Thanks,

@CEHJ: How can I capture the out of the perl command and return it in this code?

There are also methods to collect the output into StringBuilder in the same class

(at the link i posted)

So, why do I get null Pointer exception error in this code then:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class RunPerl {

        public static void runcheck() throws IOException {
            String[] perlCmd = { "which perl" };
            Runtime check_runtime = Runtime.getRuntime();
            Process check_process = null;

            try {
                check_process = check_runtime.exec(perlCmd);
                check_process.waitFor();
            } catch (Exception e) {
                System.out.println("error executing " + perlCmd[0]);
            }
            

            /* dump output stream */
            BufferedReader is = new BufferedReader
                ( new InputStreamReader(check_process.getInputStream()));
            String sLine;
            while ((sLine = is.readLine()) != null) {
                System.out.println(sLine);
            }
            System.out.flush();

            /* print final result of process */
            System.err.println("Exit status=" + check_process.exitValue());
            return;
        }
}

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And I get this error:

error executing which perl
Exception in thread "main" java.lang.NullPointerException
	at com.xxx.xxx.xxx.xxx.RunPerl.runcheck(RunPerl.java:24)

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Line 24 in the error message is actually line 22 in the code I posted above.

Because your command array should have two elements, not one. The first is the name of the app (which [must be in $PATH if it's invoked with one word like that]), the second is the argument to that app

ok. I tried a very basic command. Instead of "which perl", I put "dir". I am on a Windows platform and "dir" works on the command line

But I am getting the following error in java:

error executing dir
Exception in thread "main" java.lang.NullPointerException
	at com.xxx.xxx.xxx.xxx.RunPerl.runCheck(RunPerl.java:24)

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Line 24 has this in my code:

                ( new InputStreamReader(mwcheck_process.getInputStream()));

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do you have any idea why this does not work?

Well, I tried cmd.exe instead of dir and it did not return this error.

So , I guess my code is right. But now, I need to set the env variables and we have an internal command like "setyourenv" and I can run this command on the command line. But this does not work when I call it inside java.

How can I run any command inside Java that I run on command line?

You might need to put in the full path to setyourenv. How do you invoke it normally

I would not prefer to put the full path hard coded. Therefore, I want to get the whole environment variable. But I have some problem with it. My other open question is about that problem:

https://www.experts-exchange.com/questions/28248134/How-to-convert-environment-variable-map-from-getenv-to-string-array-for-of-name-value.html?anchorAnswerId=39518284#a39518284

As long as the command is in the path, then it shouldn't be necessary. As far as the other q is concerned, it's the same solution as your q previous to it - you must use the correct number of array elements to the command

:)