struct2args

This is a simple Python tool to convert structured data such as yaml,toml, or json to command line arguments. It is intended to allow for easy configuration of command line tools.

Installation

Homebrew coming eventually. For now you can install it with pip:

pip install struct2args

or Pipx:

pipx install struct2args

Usage

Usage is pretty straightforward. It reads a structured data file and outputs a list of command line arguments as a string. The file should have the following format:

__args__: # This is required. Each item in the list is a set of arguments.
  - _name: 'nginx-test' # The name to search for 
    name: 'nginx-test-{% gitcommit %}'
    p: '80:{% get_free_port 80 %}'
    _pos: 'nginx'
  - _name: 'nginx-detached'
    name: 'nginx-detached-{% gitcommit %}'
    p: '80:80'
    _pos:
      - '-d'
      - 'nginx'

Anything that starts with an underscore is a special command and won't be converted to an argument. The following special commands are supported:

__args__: Required in all files. This should be a list of arguments _pos*: Anything starting with _pos will be converted to a positional argument. If it is a list, each item will be interpreted as a separate positional argument.

Otherwise, all other keys will be converted to command line arguments. The key name will be the argument name and the value. So in the example above: name will be converted to --name nginx-test-{% gitcommit %}.

To use the tool you can run it two ways:

1. Command line to xargs

```bash
struct2args <file> | xargs <command>
```

2. Passing in a --cmd argument

```bash
struct2args --cmd <command> <file>
```

Jinja2 Templating

The tool uses Jinja2 templating to allow for dynamic arguments. The standard functions are available as well as the ones from jinja2-git.

In addition, there is a custom tag of get_free_port. This will return a free port on the host machine starting at the port number specified. For example, {% get_free_port 80 %} will return a free port starting at 80. This is useful for things like port forwarding. You can declare a maximum port number by passing in an optional second argument. For example {% get_free_port 80 90 %} will return a free port between 80 and 90.