Cron作业未运行jar

Question

This is my Java file for which I have created Delete.jar

import java.io.*;

public class Delete {
 public static void main(String[] args)
    {
        try{
            int i =1;
            while(i<5){
                File directory = new File("downloads");
                System.out.println("I am running");
                for(File file: directory.listFiles()) file.delete();
                i++;
             }
        }catch(Exception e){

                e.printStackTrace();

        }

    }
}

This is my Script to run the jar file if it is not running

#!/bin/bash
processid=`pgrep -f 'Delete.jar high'`
echo "Processes:"$processid
if [ -n "$processid" ]
then
echo "Process is running. No action will be taken"
else
echo "Process is not running. Executing ResponseHandler-fast now !"
cd /home/ubuntu/;
java -jar Delete.jar high
fi

This is line I have added to my crontab -e

* * * * * sh /home/ubuntu/check.sh

I rebooted my System I was expecting that my script will run check that jar is not running and it will run it but it is not doing so. What I am doing wrong here.

If I execute ps after 2 -3 minutes still I am not getting java as an entry.

Thanks.

Answer 1

Please send output of your shell script to a log file as shown below(make changes to your crontab entry):

* * * * * sh /home/ubuntu/check.sh >> /home/ubuntu/output.log 2>&1

In this way, you will know what exactly is being run and then finding the exact cause will become easier.

Answer 2

Did you try running /home/ubuntu/check.sh manually? May be it's not finding the jar file or even java program.

Answer 3

Cron doesn't magically make the program "run forever". Start the program manually. It will probably take 1-2 seconds to run, then exit. This is exactly what happens when running with cron, as well. So, unless you run ps the second your program gets started, you won't see anything in the process list.

Your loop 1..5 won't help, as after the files are deleted in the first round, the rest is effectively a no-op.