unable to run shell script in mac os thru java program

Question

I'm trying to run shell script thru Java in Mac OS. The shell script has git clone command clone a repository.

I have tried using process builder API. It's not giving any exception though but the repo is not cloning when I run the code.

public class Test {
public static void main(String[] args) throws IOException  {

    Process p;
    try {

        List<String> cmdList = new ArrayList<String>();

        cmdList.add("/Users/Folder/AnotherFolder/Another/Final/clone.sh");
        ProcessBuilder pb = new ProcessBuilder(cmdList);
        p = pb.start();

        p.waitFor(); 
        BufferedReader reader=new BufferedReader(new InputStreamReader(
                p.getInputStream())); 
        String line; 
        while((line = reader.readLine()) != null) { 
            System.out.println(line);
        } 
    } catch (Exception e) {

        e.printStackTrace();
        System.out.println(e.getMessage());
    } 
}

}

Expecting to clone git project in the path, but not giving any output or Exception.

sreekesh.s · Accepted Answer · 2019-10-17 17:17:59Z

1

Above JAVA code works fine, I suspect there could be some issue with the script.Because git local repo will not be know when java program tries to execute the shell script.

On executing program with below script git clone works fine.

#!/bin/bash
mkdir ~/repo
cd ~/repo
git init
#git config user.email "email"
#git config user.name "user"
/usr/local/bin/git clone https://github.com/divaibhav/helloworld

edited Oct 17, 2019 at 17:17

answered Oct 17, 2019 at 17:06

sreekesh.s

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1 Comment

ramkr Over a year ago

Thanks! looks like git init is needed before doing the clone in the path

VGR · Accepted Answer · 2019-10-17 18:37:02Z

0

You are ignoring any error messages emitted by your script.

Remove all use of p.getInputStream(), and replace it with a call to inheritIO():

try {
    ProcessBuilder pb = new ProcessBuilder(
        "/Users/Folder/AnotherFolder/Another/Final/clone.sh");

    pb.inheritIO();

    p = pb.start();
    p.waitFor();
} catch (IOException | InterruptedException) {
    e.printStackTrace();
}

When you were calling p.getInputStream(), you were only reading the standard output of the process. inheritIO() will cause both the standard output and the standard error of the child process to appear in the Java process's own standard output and standard error. This will allow you to see all diagnostic messages printed by the script. In particular, error messages usually appear on standard error, not standard output.

answered Oct 17, 2019 at 18:37

VGR

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3 Comments

user11861129 Over a year ago

If you use RunTime.exec(commandAsString), you will receive two InputStreams, one for Standard Output and the second for Standard Error. I have not checked whether or not RunTime.exec(...) will execute a Shell ".sh". though... And I am away from my computer right now on a cell. Getting both InputStreams (for me) helps a lot - because you can check when an error occurs.

VGR Over a year ago

@Torelló大哥 You can read them separately, but inheritIO() is a lot easier. And programs really should use ProcessBuilder instead of Runtime.exec.

user11861129 Over a year ago

I have not used ProcessBuilder, I guess I will try it sometime. The trade-off, obviously is - you get to know when your underlying UNIX commands fail. And YES it makes the code more complicated. But that's what library routines are good for. Write once, forget about it... :). Note: I used to (but not really anymore) have a lot of tar -cvf commands that would mysteriously "not work". Paying attention (explicitly) to StdError caught bugs. Yes, it's kind of a pain

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