Calling bash script with redirection from Java

I have a bash shell script that executes a bunch of commands and redirects the command outputs to log files using >. If I call the shell script from Java using Runtime.getRuntime().exec("sh shellscript.sh");, the shell script gets executed but the log files don't get written! Why? And how do I make it work?

EDIT: Okay so what I'm trying to do is a little different. Your code works fine. But now redirection inside the Java program is not working. In the sample program below, the log file is not written!

$ cat 开发者_开发百科script.sh 
#!/bin/sh

echo "Hello there"
echo "Hello there 2"


$ cat RunScript.java 
public class RunScript {
    public static void main(String[] argv) throws Exception {
        int i = Runtime.getRuntime().exec("sh /home/gpx/script.sh >> log").waitFor();
        System.out.println("Exit code : " + i);
    }
}

The redirects that you are writing to - are they writing to absolute file paths or relative file pahts?

If its relative, then they would (probably) be relative to the work directory - so check that.

A SAMPLE TEST I DID THAT SHOWS ABSOLUTE PATHS WILL WORK

$ cat script.sh 
#!/bin/sh

echo "Hello there"
echo "Hello there 2" >> /Users/madhurt/test/log

exit 2

$ cat RunScript.java 
public class RunScript {
    public static void main(String[] argv) throws Exception {
        int i = Runtime.getRuntime().exec("sh /Users/madhurt/test/script.sh").waitFor();
        System.out.println("Exit code : " + i);
    }
}
$ pwd
/Users/madhurt/test
$ ls -lrt 
total 24
-rwxr-xr-x  1 madhurt  staff   87 Dec  6 18:28 script.sh
-rw-r--r--  1 madhurt  staff  214 Dec  6 18:32 RunScript.java
-rw-r--r--  1 madhurt  staff  907 Dec  6 18:32 RunScript.class
$ java RunScript
Exit code : 2
$ ls -lrt 
total 32
-rwxr-xr-x  1 madhurt  staff   87 Dec  6 18:28 script.sh
-rw-r--r--  1 madhurt  staff  214 Dec  6 18:32 RunScript.java
-rw-r--r--  1 madhurt  staff  907 Dec  6 18:32 RunScript.class
-rw-r--r--  1 madhurt  staff   14 Dec  6 18:33 log
$ cat log 
Hello there 2
$ 

My Java-knowledge is scant, but it's my understanding that you have to write:

Runtime.getRuntime().exec("sh shellscript.sh").waitFor();

Check if you have write permissions to the path you are appending the log too. If you run this app within a container, it will most likely use that user's id. Try to write the file in /tmp/ and see if it appears there.