How to return a value from java to script

[ramjcp kris]

Hi All

my Requirement is I need to return a value from java program to a shell script.my main class is being called from this shell script;

following is my test.sh

  java com.sample.Hello  

And my Hello class code is below

 class Hello{
public static void main(String [] args) {
System.exit(12);
}
}
   

can any one tell me how to print the value returned from my java program to shell script
waiting for reply with anticipation

[Freddy Wong]

I don't quite understand your question In your code Java code, it doesn't seem to print anything. If you invoke test.sh, of course you won't see anything.

If let's say you have a Hello World program, then you run it from your script, I'm pretty sure you can see the Hello World message in your shell.

[Sri Anand]

you can save the property in a file and retrieve either from java or shell. if this is not too much for what you are trying to achieve

[Ulf Dittmer]

While it's possible to use System.exit to pass a value to the shell, that's meant for status codes. If the program runs to completion without error, then it should return a 0 to the shell.

The standard approach would be to print the value to standard out. What kind of shell are you using?

[Harjit Singh]

The way you can to it

1) when you are calling this class from the shell script. Redirect the output to a file

java my.class > out.txt

in the shell script you can read this value from the file

In the java class write it to the output stream using system.out

Hope that helps

- H

[Stefan Wagner]

I agree with Ulf.
If you ignore the hint, you catch the exit code with $? (at least bash works that way):

java com.sample.Hello  
result=$?
echo $result

But returncode not 0 indicates an error, and the wrong approach to return a correct result.
If the program fails, you can't recognize this anymore, and if you use it in a script, everybody is confused.

The right way is indeed to use System.out.println (result); and read that value, but of course without the detour of writing to a file:

result=$(java com.sample.Hello)

nice and easy - isn't it?

[Edmundo Carmona]

...or you can throw whatever you want to STDOUT (System.out, you know, right?) and from the bash side use "while read variable" to get the output and work on it:

Example (not java related):
$ dmesg | while read line; do echo $line; done

replace dmesg for the java command to run your application and enjoy!