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Setting Environment variables and then running a perl script from a java program.

Posted on 2001-09-18
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Last Modified: 2008-02-01
I am trying to run perl script called mib2c for UCD-SNMP on Linux. To automate the process , I want to have a java program that does the following:

1.   Sets an environment variable i.e export MIBS=ALL

2. Runs the perl script with the above settings i.e /root/snmp/ucd-snmp-4.1.2/local/mib2c <options>.

I thought that I could do the above using Runtime class like :

Runtime myRuntime = Runtime.getRuntime();
Process myProcess = myRuntime.exec("export MIBS=ALL");
and then use the output stream of the "myProcess" to pass the command for running the perl script.

However , I realised that this is not possible as I get the following message when I read the error streams of the process:

export: local server: Call timed out
export: MIBS=ALL: No such file or directory

Another approach could be to  to open a socket on port 23(i.e telnet session) and then give login and password and then pass the commands. However , I want this to be my last resort as this would require password etc. which would decrease the security + the code would be bulky.

Can anyone provide a solution for my problem?
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Question by:Siddhartha_s
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7 Comments
 
LVL 1

Expert Comment

by:Lab_Rat
ID: 6490753
I think you can settthe "export MIBS=ALL" in a batchfile that sets that environment variable.



something like:

(SetAll.Bat)
set MIBS=ALL


then use (erm!, i think you would need some kind of batchfile parser here, maybe command.com?)

Process myProcess=myRuntime.exec("SetAll.Bat");


Erm, this could help with the enviroment variable. But it's early and I could be way off here.
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LVL 19

Expert Comment

by:Jim Cakalic
ID: 6490754
There are several variants of the exec method that take String[] or environment variable settings in the form "name=value" that will be supplied to the new process.
    http://java.sun.com/j2se/1.3/docs/api/java/lang/Runtime.html

Jim
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Expert Comment

by:ManojShetty
ID: 6491125

To set the environment variable
 System.setProperty(key, Value)

To access it use System.getProperty(key);
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LVL 19

Accepted Solution

by:
Jim Cakalic earned 200 total points
ID: 6491441
Here are a couple classes that might help you. The first, Environment, gets the OS environment. It doesn't use JNI but it does assume the command env exists. This is not completely platform-independent. The second, Launch, calls the Runtime.exec method I alluded to earlier. It instantiates an Environment object and adds to it any name=value pairs that are found in the command line arguments. The last command-line argument to Launch should be the command that you want to execute.

Best regards,
Jim Cakalic

---------- Environment.java ----------
import java.io.*;
import java.util.*;

public class Environment {
    private Properties _props;

    public Environment() {
        _props = new Properties();
        try {
            Runtime rt = Runtime.getRuntime();
            Process proc = rt.exec("env");
            InputStream in = proc.getInputStream();
            _props.load(in);
            in.close();
            proc.destroy();
        } catch (Exception e) {
        }
    }
    public String get(String key) {
        return _props.getProperty(key);
    }
    public String get(String key, String fallback) {
        return _props.getProperty(key, fallback);
    }
    public void set(String key, String val) {
        _props.setProperty(key, val);
    }
    public String[] get() {
        String[] values = new String[_props.size()];
        Enumeration each = _props.keys();
        for (int i = 0; each.hasMoreElements(); ++i) {
            String key = (String)each.nextElement();
            String value = _props.getProperty(key);
            values[i] = key + "=" + value;
        }
        return values;
    }

    public static void main(String[] args) throws Exception {
        Environment env = new Environment();
        String[] values = env.get();
        for (int i = 0; i < values.length; ++i) {
            System.out.println(values[i]);
        }
    }
}
---------- end ----------

---------- Launch.java ----------
import java.io.*;

public class Launch {
    public static void main(String[] args) throws Exception {
        Environment env = new Environment();
        for (int i = 0; i < args.length - 1; ++i) {
            String arg = args[i];
            int index;
            if ((index = args[i].indexOf("=")) >= 0) {
                String key = arg.substring(0, index).trim();
                String value = arg.substring(index + 1).trim();
                env.set(key, value);
            }
        }
        Runtime rt = Runtime.getRuntime();
        Process proc = rt.exec(args[args.length - 1], env.get());
        InputStream in = proc.getInputStream();
        while (in.read() >= 0) {
        }
        proc.waitFor();
    }
}
---------- end ----------
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Expert Comment

by:Venabili
ID: 8932736
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

- Points for jim_cakalic

Please leave any comments here within the next seven days.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

Venabili
EE Cleanup Volunteer
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Expert Comment

by:Jim Cakalic
ID: 8934086
OK. Thanks. :-)
Jim
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