127 lines
2.9 KiB
Markdown
127 lines
2.9 KiB
Markdown
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---
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title: "Python: How to easily write a CLI tool for Linux using Fire"
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date: "2023-04-09"
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---
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I want to share the easiest way I know to write a CLI tool for Linux administration
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using python and Fire.
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## Step 1: Install Fire
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```bash
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pip install fire
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```
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## Step 2. Create a simple CLI tool
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Here is an example of a CLI tool that prints the Linux version to the terminal:
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<!--more-->
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```python
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#!/usr/bin/env python3
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import fire
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import platform
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class SysInfo:
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"""A CLI tool for getting system information about Linux server"""
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def kernel(self):
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"""A method for getting kernel version"""
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version = platform.release()
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return f"Kernel version: {version}"
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if __name__ == "__main__":
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obj = SysInfo()
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fire.Fire(obj)
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```
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Paste this code into a file called `my-cli-tool` and give it permission to execute:
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```bash
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chmod +x my-cli-tool
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```
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Then put this file in the path `/usr/local/bin`:
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```bash
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sudo cp ./my-cli-tool /usr/local/bin
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```
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To use this tool, just type the command:
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```bash
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my-cli-tool kernel
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```
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You will see output like this:
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```plaintext
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❯ my-cli-tool kernel
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Kernel version: 6.2.2-060202-generic
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```
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As you can see, it is enough to create a class, a method(s) in it, and pass the class object to the fire.Fire() function - and the cli tool is ready!
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This will automatically generate a help page, which can be called using the `--help` flag:
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```bash
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my-cli-tool --help
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```
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You will get this output:
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```plaintext
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NAME
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my-cli-tool - A CLI tool for getting system information about Linux server
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SYNOPSIS
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my-cli-tool COMMAND
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DESCRIPTION
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A CLI tool for getting system information about Linux server
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COMMANDS
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COMMAND is one of the following:
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kernel
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A method for getting kernel version
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```
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## Making the tool more complex
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For example, we also want our tool to be able to print the kernel version in short form, like this: `6.2.2`.
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We rewrite the code as follows:
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```python
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#!/usr/bin/env python3
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import fire
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import platform
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class SysInfo:
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"""A CLI tool for getting system information about Linux server"""
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def kernel(self, format: ("short", "full") = "full"):
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"""A method for getting kernel version"""
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version = platform.release()
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if format == "short":
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return version.split("-")[0]
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return f"Kernel version: {version}"
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if __name__ == "__main__":
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obj = SysInfo()
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fire.Fire(obj)
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```
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Now we can type the following command:
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```bash
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my-cli-tool kernel --format short
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```
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Output:
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```plaintext
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6.2.2
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```
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This will also automatically update the help page, adding the `--format` flag and its possible values:
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```bash
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my-cli-tool kernel --help
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```
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Output:
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```plaintext
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NAME
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my-cli-tool kernel - A method for getting kernel version
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SYNOPSIS
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my-cli-tool kernel <flags>
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DESCRIPTION
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A method for getting kernel version
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FLAGS
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-f, --format=FORMAT
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Type: ('short', 'full')
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Default: 'full'
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```
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