ProcessBuilder environment variable in java

Question

I\'m trying to add a environment variable for a ProcessBuilder object but then when I call on that new variable in the ProcessBuilder I get an error. this is how I build the

Answer 1

Alfredo O's example gives you the right idea. You need to tell the ProcessBuilder what program to use to execute your command. In this case bash with the "-c" switch, which tells bash to interpret what comes next (i.e. "echo $u") as a command.

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Map;

public class OTU {
    public static void main(String[] args) throws Exception {
        ProcessBuilder pb = new ProcessBuilder("/bin/bash", "-c", "echo $u");
        Map env = pb.environment();
        // set environment variable u
        env.put("u", "util/");

        Process p = pb.start();
        String output = loadStream(p.getInputStream());
        String error = loadStream(p.getErrorStream());
        int rc = p.waitFor();
        System.out.println("Process ended with rc=" + rc);
        System.out.println("\nStandard Output:\n");
        System.out.println(output);
        System.out.println("\nStandard Error:\n");
        System.out.println(error);
    }

    private static String loadStream(InputStream s) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(s));
        StringBuilder sb = new StringBuilder();
        String line;
        while ((line = br.readLine()) != null)
            sb.append(line).append("\n");
        return sb.toString();
    }
}

This produces the following output:

Process ended with rc=0

Standard Output:

util/


Standard Error: