Command line interaction using Ruby

Question

I have a Rails application and am trying to communicate with a Java program via the CLI.

When I run the Java code using system :

system "java askQuestion"

it prompts for user input and waits for an answer, such as "What is your age?"

I want to pass a value in from a variable, and capture the output.

How can I interact with the CLI and run the command?

I did research but I couldn't find anything or I missed the correct term to search.

Solution: IO.popen

update --> I found here what exactly I want and share maybe help someone else too , http://ruby.bastardsbook.com/chapters/external-programs/

Answer 1

Kernel#system just executes the command in a subshell, returning the result ( true / false ) of process start.

To catch the output, use backticks (or %x|| ) .

To interact with a shell, one might use IO#popen , but in your case I would just stick to executing

output = `echo 37 | java askQuestion`

The above will pass the output of echo (37 in this particular case) to the Java process. The response of the Java process will be stored in the output variable.