Organizations are moving to physical and virtual infrastructure-as-code environments, a shift that makes configuration files vital for managing devices. Key file formats include TOML and INI.
This article examines both languages, presenting advice about uses, benefits, editing and management. Use the information here to determine whether your infrastructure code should rely on one of these languages.
Introducing TOML and INI files
TOML is the configuration language of choice for various programming languages, including Python and Rust. Python tools, like pytest and mypy, rely on TOML configuration files, and the Rust Cargo build system/package manager also uses TOML. Administrators rely on TOML in various infrastructure contexts, including containerd, AWS Serverless Application Model and Cloud Native Buildpacks.
TOML features a structure with key-value pairs that are simple and readable. It supports various data types and uses clear language to facilitate easy construction and troubleshooting. TOML works well with many common programming languages, such as JavaScript, Java, C# and PHP. These configuration files use the .toml file extension. It’s less common in infrastructure or system configuration scenarios.
Like TOML, administrators frequently use the INI format to manage deployment options or software settings. While initially an MS-DOS and Windows tool, modern utilities, like Git and Linux’s systemd, still use it today.
INI files are widely supported. They work well for general system and network device configuration. They also feature good readability and relatively easy troubleshooting.
Syntax comparison
TOML primarily utilizes key-value pairs as its configuration settings, with each pair separated by an equal sign. Related values include strings, integers, Booleans or dates. Keys can be letters, numbers, underscores or dashes. TOML identifies comments as lines beginning with the # character. Note that TOML ignores white spaces in the file and is case-sensitive, so pay careful attention when authoring configuration files.
INI files are divided into sections denoted by text inside square brackets, such as [section]. As with other languages, INI files specify settings for various items using a key-value pair. The hashtag and semicolon denote comments. INI files also ignore blank lines, which enhances readability.
Other syntax rules for INI include the following:
- Is case-insensitive.
- Uses double quotes around values containing spaces, such as surrounding “example one” with double quotes.
- Escapes special characters, including equal signs, colon and square brackets. The backslash character escapes these values.
Many INI file parsers exist, and the language is not strictly defined. There might be implementation-specific rules or exceptions.
Working with TOML and INI files
Popular text editors and coding tools usually support TOML structures and validation, and INI’s straightforward syntax means most text editors can handle it. Here are a few editors to consider:
- Notepad++.
- Sublime Text.
- Vim and vim-toml plugin.
- Visual Studio Code/VSCodium.
Look for additional plugins or extensions that support the configuration language in use.
Version control
Most organizations rely on Git or a similar repository to manage development projects, application code and other essential files. Regardless of the file format, incorporate the one in use into a version control system.
File security
Maintaining the security and integrity of configuration files is paramount. Many of the same practices that manage source files remain crucial. Here are a few specifics to keep in mind:
- Evaluate and test all configuration files.
- Use version control to maintain settings.
- Use and distribute digitally signed TOML and INI configuration files.
- Use only TOML, INI and other configuration files from trusted sources.
These practices ensure files are up to date, secure and configured according to the user’s specifications.
TOML’s advantages and disadvantages
The main drawback to TOML is that configuration languages, like XML, handle more complex data structures better. TOML is also not as widespread as YAML or JSON.
Many developers find TOML easier to read and edit than JSON, XML and YAML. TOML’s structure is less complex than YAML, making it more predictable and less likely to change.
TOML advantages include the following:
- Readability.
- Broad support.
- Simple comments.
- Straightforward error messages.
- Simplicity that makes authoring files quicker.
- Generally faster parsing than YAML but slower than JSON.
INI’s advantages and disadvantages
Like TOML, INI also does not handle complex data structures like XML. INI has more limitations than languages like TOML, JSON or YAML. However, INI files are usually more straightforward than other languages as they are simpler to write, edit and troubleshoot.
Consider the following before using INI files:
- Structure is limited to key-value pairs.
- Readability makes results more predictable.
- Less hierarchy is available for complex instructions.
- Lack of standardization means some files may be more challenging to work with.
Damon Garn owns Cogspinner Coaction and provides freelance IT writing and editing services. He has written multiple CompTIA study guides, including the Linux+, Cloud Essentials+ and Server+ guides, and contributes extensively to TechTarget Editorial, The New Stack and CompTIA Blogs.
