How to Get Output from Command in Java: stty size Example

Discover how to capture command output in Java with this simple guide, focusing on `stty size` to retrieve terminal dimensions.
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This video is based on the question https://stackoverflow.com/q/69830611/ asked by the user 'James Dougan' ( https://stackoverflow.com/u/17322021/ ) and on the answer https://stackoverflow.com/a/69831889/ provided by the user 'vanje' ( https://stackoverflow.com/u/459557/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Get Output from Command in Java: stty size Example

When working on Java projects, one of the common tasks might be to interact with the operating system or retrieve system information. A frequently asked question is: How do you get output from a command in Java? This can be particularly useful when you need to get specific information such as the size of the terminal window, which you can obtain using the command stty size. In this guide, we will break down how to effectively execute this command in Java and retrieve its output.

Understanding the Problem

In your Java project, you might want to use the stty size command to get the dimensions of the terminal window, which gives you output in rows and columns, such as 30 213. However, executing this command through Java can often lead to unexpected results, for instance, receiving an output like [I-6ce253f1, which is not at all helpful. This issue usually arises from how the command output is being processed and printed.

Step-by-Step Solution

Here is a solution to capture the output from the stty size command effectively in Java. We will use a ProcessBuilder for executing the command and use input and error stream redirection for better handling of any error outputs.

1. Setting Up ProcessBuilder

To start, you want to create a ProcessBuilder object to run the stty size command. Below is the code snippet that you can use:

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2. Starting the Process

Once you have your ProcessBuilder set up, you can start the process and read its output using an InputStreamReader and a BufferedReader. Here’s how to do that:

[[See Video to Reveal this Text or Code Snippet]]

3. Understanding Input and Error Stream Redirection

Redirecting Error Stream: By calling processBuilder.redirectErrorStream(true);, any error messages generated by the command will be output through the same stream. This can provide you with more comprehensive feedback, helping you diagnose any issues that may arise from the command you are running.

Input Channel: Using processBuilder.redirectInput(ProcessBuilder.Redirect.INHERIT); allows your Java process to inherit the input channel of the terminal. This is particularly useful when the command being run may need to interact with user input.

Conclusion

By following these steps, you will be able to capture and display the output from the stty size command in Java effectively. This technique can easily be adapted for other terminal commands and used in various Java projects where you need to interact with system-level operations. Remember that handling streams correctly is crucial in ensuring you receive the correct output without errors.

If you still run into issues, double-check the permissions and the environment where your Java application is running, as these can also affect command execution.

Feel free to implement this solution in your project and enjoy seamless command execution in Java!

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