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Build Status Crates.io Crates.io Released API docs Maintenance

This crate provides the Ini struct which implements a basic configuration language which provides a structure similar to what’s found in Windows' ini files. You can use this to write Rust programs which can be customized by end users easily.

This is a simple configuration parsing utility with no dependencies built on Rust. It is inspired by Python's configparser.

The current release is stable and changes will take place at a slower pace. We'll be keeping semver in mind for future releases as well.

🚀 Quick Start

A basic ini-syntax file (we say ini-syntax files because the files don't need to be necessarily *.ini) looks like this:

key1 = value1
pizzatime = yes
cost = 9

nuclear launch codes = topsecret

User = QEDK

Essentially, the syntax consists of sections, each of which can which contains keys with values. The Ini struct can read and write such values to strings as well as files.

🧰 Installation

You can install this easily via cargo by including it in your Cargo.toml file like:

configparser = "3.0.4"

➕ Supported datatypes

configparser does not guess the datatype of values in configuration files and stores everything as strings. However, some datatypes are so common that it‘s a safe bet that some values need to be parsed in other types. For this, the Ini struct provides easy functions like getint(), getuint(), getfloat() and getbool(). The only bit of extra magic involved is that the getbool() function will treat boolean values case-insensitively (so true is the same as True just like TRUE). The crate also provides a stronger getboolcoerce() function that parses more values (such as T, yes and 0, all case-insensitively), the function’s documentation will give you the exact details.

use configparser::ini::Ini;

let mut config = Ini::new();
  someintvalue = 5"));
let my_value = config.getint("somesection", "someintvalue").unwrap().unwrap();
assert_eq!(my_value, 5); // value accessible!

//You can ofcourse just choose to parse the values yourself:
let my_string = String::from("1984");
let my_int = my_string.parse::<i32>().unwrap();

📝 Supported ini file structure

A configuration file can consist of sections, each led by a [section-name] header, followed by key-value entries separated by a delimiter (= and :). By default, section names and key names are case-insensitive. Case-sensitivity can be enabled using the Ini::new_cs() constructor. All leading and trailing whitespace is removed from stored keys, values and section names. Key values can be omitted, in which case the key-value delimiter may also be left out (but this is different from putting a delimiter, we'll explain it later). You can use comment symbols (; and # to denote comments). This can be configured with the set_comment_symbols() method in the API. Keep in mind that key-value pairs or section headers cannot span multiple lines. Owing to how ini files usually are, this means that [, ], =, :, ; and # are special symbols by default (this crate will allow you to use ] sparingly).

Let's take for example:

[section headers are case-insensitive by default]
[   section headers are case-insensitive by default   ]
are the section headers above same? = yes
sectionheaders_and_keysarestored_in_lowercase? = yes
keys_are_also_case_insensitive = Values are case sensitive
Case-sensitive_keys_and_sections = using a special constructor
you can also use colons : instead of the equal symbol
;anything after a comment symbol is ignored
#this is also a comment
spaces in keys=allowed ;and everything before this is still valid!
spaces in values=allowed as well
spaces around the delimiter = also OK

[All values are strings]
values like this= 0000
or this= 0.999
are they treated as numbers? = no
integers, floats and booleans are held as= strings

this key has an empty string value has Some("") =

    [indented sections]
        can_values_be_as_well = True
        purpose = formatting for readability
        is_this_same     =        yes

An important thing to note is that values with the same keys will get updated, this means that the last inserted key (whether that's a section header or property key) is the one that remains in the HashMap. The only bit of magic the API does is the section-less properties are put in a section called “default”. You can configure this variable via the API. Keep in mind that a section named “default” is also treated as sectionless so the output files remains consistent with no section header.

🛠 Usage

Let's take another simple ini file and talk about working with it:

KFC = the secret herb is orega-

Uint = 31415

If you read the above sections carefully, you‘ll know that 1) all the keys are stored in lowercase, 2) get() can make access in a case-insensitive manner and 3) we can use getuint() to parse the Uint value into an u64. Let’s see that in action.

use configparser::ini::{Ini, WriteOptions};
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>> {
  let mut config = Ini::new();

  // You can easily load a file to get a clone of the map:
  let map = config.load("tests/test.ini")?;
  println!("{:?}", map);
  // You can also safely not store the reference and access it later with get_map_ref() or get a clone with get_map()

  // If you want to access the value, then you can simply do:
  let val = config.get("TOPSECRET", "KFC").unwrap();
  // Notice how get() can access indexes case-insensitively.

  assert_eq!(val, "the secret herb is orega-"); // value accessible!

  // What if you want remove KFC's secret recipe? Just use set():
  config.set("topsecret", "kfc", None);

  assert_eq!(config.get("TOPSECRET", "KFC"), None); // as expected!

  // What if you want to get an unsigned integer?
  let my_number = config.getuint("values", "Uint")?.unwrap();
  assert_eq!(my_number, 31415); // and we got it!
  // The Ini struct provides more getters for primitive datatypes.

  // You can also access it like a normal hashmap:
  let innermap = map["topsecret"].clone();
  // Remember that all indexes are stored in lowercase!

  // You can easily write the currently stored configuration to a file with the `write` method. This creates a compact format with as little spacing as possible:

  // You can write the currently stored configuration with different spacing to a file with the `pretty_write` method:
  let write_options = WriteOptions::new_with_params(true, 2, 1);
  // or you can use the default configuration as `WriteOptions::new()`
  config.pretty_write("pretty_output.ini", &write_options);

  // If you want to simply mutate the stored hashmap, you can use get_mut_map()
  let map = config.get_mut_map();
  // You can then use normal HashMap functions on this map at your convenience.
  // Remember that functions which rely on standard formatting might stop working
  // if it's mutated differently.

  // If you want a case-sensitive map, just do:
  let mut config = Ini::new_cs();
  // This automatically changes the behaviour of every function and parses the file as case-sensitive.


The Ini struct offers great support for type conversion and type setting safely, as well as map accesses. See the API for more verbose documentation.


  • indexmap: Activating the indexmap feature allows using indexmap in place of HashMap to store the sections and keys. This ensures that insertion order is preserved when iterating on or serializing the Ini object. Due to the nature of indexmap, it offers mostly similar performance to stdlib HashMaps but with slower lookup times.

You can activate it by adding it as a feature like this:

configparser = { version = "3.0.4", features = ["indexmap"] }
  • tokio: Activating the tokio feature adds asynchronous functions for reading from (load_async()) and writing to (write_async()) files using tokio.

You can activate it by adding it as a feature like this:

configparser = { version = "3.0.4", features = ["tokio"] }

📜 License

Licensed under either of

at your option.

✏ Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the LGPL-3.0 license, shall be dual licensed as above, without any additional terms or conditions.

🆕 Changelog

Old changelogs are in CHANGELOG.md.

  • 3.0.0
    • 😅 BREAKING IniDefault is now a non-exhaustive struct, this will make future upgrades easier and non-breaking in nature. This change might also have a few implications in updating your existing codebase, please read the official docs for more guidance.
    • IniDefault is now internally used for generating defaults, reducing crate size.
    • 🚀 There is now a new optional indexmap feature that preserves insertion order of your loaded configurations.
  • 3.0.1
    • Uses CRLF line endings for Windows files.
    • Bumps crate to 2021 edition.
    • Adds features to CI pipeline.
  • 3.0.2
    • Adds support for multi-line key-value pairs.
    • Adds async-std feature for asynchronous file operations.
    • Some performance optimizations.
  • 3.0.3
    • Add default empty line on empty strings.
    • Feature to append to existing Ini objects.
    • Minor lint fixes.
  • 3.0.4 (STABLE)
    • Adds pretty printing functionality
    • Replaces async-std with tokio as the available async runtime
    • The async-std feature will be deprecated in a future release

🔜 Future plans

  • Support for appending sections, coercing them as well.
  • Benchmarking against similar packages.