robius-directories

Introduction

• A fork of the directories crate that supports Android via the robius-android-env crate

• a tiny mid-level library with a minimal API

• that provides the platform-specific, user-accessible locations

• for retrieving and storing configuration, cache and other data

• on Linux, Redox, Windows (≥ Vista), macOS and other platforms.

The library provides the location of these directories by leveraging the mechanisms defined by

• the XDG base directory and the XDG user directory specifications on Linux
• the Known Folder API on Windows
• the Standard Directories guidelines on macOS
• the Context SDK APIs on Android
  • Specifically, getFilesDir() and getCacheDir()

Platforms

This library is written in Rust, and supports Linux, Redox, macOS, Windows, and Android. Other platforms are also supported; they use the Linux conventions.

dirs, the low-level sister library, is available at dirs-rs.

A version of this library running on the JVM is provided by directories-jvm.

Usage

Dependency

Add the library as a dependency to your project by inserting

robius-directories = "5.0"

into the [dependencies] section of your Cargo.toml file.

If you are upgrading from version 2, please read the section on breaking changes first.

Example

Library run by user Alice:

extern crate robius_directories;
use robius_directories::{BaseDirs, UserDirs, ProjectDirs};

if let Some(proj_dirs) = ProjectDirs::from("com", "Foo Corp",  "Bar App") {
    proj_dirs.config_dir();
    // Lin: /home/alice/.config/barapp
    // Win: C:\Users\Alice\AppData\Roaming\Foo Corp\Bar App\config
    // Mac: /Users/Alice/Library/Application Support/com.Foo-Corp.Bar-App
    // Android: /data/.../org.Baz-Corp.Foo-Bar-App/files
}

if let Some(base_dirs) = BaseDirs::new() {
    base_dirs.executable_dir();
    // Lin: Some(/home/alice/.local/bin)
    // Win: None
    // Mac: None
    // Android: None
}

if let Some(user_dirs) = UserDirs::new() {
    user_dirs.audio_dir();
    // Lin: /home/alice/Music
    // Win: C:\Users\Alice\Music
    // Mac: /Users/Alice/Music
    // Android: None
}

Design Goals

• The directories library is designed to provide an accurate snapshot of the system's state at the point of invocation of BaseDirs::new, UserDirs::new or ProjectDirs::from.
  Subsequent changes to the state of the system are not reflected in values created prior to such a change.
• This library does not create directories or check for their existence. The library only provides information on what the path to a certain directory should be.
  How this information is used is a decision that developers need to make based on the requirements of each individual application.
• This library is intentionally focused on providing information on user-writable directories only, as there is no discernible benefit in returning a path that points to a user-level, writable directory on one operating system, but a system-level, read-only directory on another.
  The confusion and unexpected failure modes of such an approach would be immense.
  • executable_dir is specified to provide the path to a user-writable directory for binaries.
    As such a directory only commonly exists on Linux, it returns None on macOS and Windows.
  • font_dir is specified to provide the path to a user-writable directory for fonts.
    As such a directory only exists on Linux and macOS, it returns None on Windows.
  • runtime_dir is specified to provide the path to a directory for non-essential runtime data. It is required that this directory is created when the user logs in, is only accessible by the user itself, is deleted when the user logs out, and supports all filesystem features of the operating system.
    As such a directory only commonly exists on Linux, it returns None on macOS and Windows.

Features

BaseDirs

The intended use case for BaseDirs is to query the paths of user-invisible standard directories that have been defined according to the conventions of the operating system the library is running on.

If you want to compute the location of cache, config or data directories for your own application or project, use ProjectDirs instead.

UserDirs

The intended use case for UserDirs is to query the paths of user-facing standard directories that have been defined according to the conventions of the operating system the library is running on.

ProjectDirs

The intended use case for ProjectDirs is to compute the location of cache, config or data directories for your own application or project, which are derived from the standard directories.

The specific value of <project_path> is computed by the

ProjectDirs::from(qualifier: &str,
                  organization: &str,
                  application: &str)

function and varies across operating systems. As an example, calling

ProjectDirs::from("org"         /*qualifier*/,
                  "Baz Corp"    /*organization*/,
                  "Foo Bar-App" /*application*/)

results in the following values:

Note that on Android, the passed-in parameters of qualifier, organization, and application are ignored because they are pre-determined by the Android application's package name, and cannot be chosen at runtime.

The ProjectDirs::from_path function allows the creation of ProjectDirs structs directly from a PathBuf value. This argument is used verbatim and is not adapted to operating system standards.

The use of ProjectDirs::from_path is strongly discouraged, as its results will not follow operating system standards on at least two of three platforms.

Comparison

There are other crates in the Rust ecosystem that try similar or related things. Here is an overview of them, combined with ratings on properties that guided the design of this crate.

Please take this table with a grain of salt: a different crate might very well be more suitable for your specific use case. (Of course my crate achieves my design goals better than other crates, which might have had different design goals.)

• Lin: Linux support
• Mac: macOS support
• Win: Windows support
• Android: Android support
• Base: Supports generic base directories
• User: Supports user directories
• Proj: Supports project-specific base directories
• Conv: Follows naming conventions of the operating system it runs on

Build

It's possible to cross-compile this library if the necessary toolchains are installed with rustup. This is helpful to ensure a change has not broken compilation on a different platform.

The following commands will build this library on Linux, macOS, Windows, Android, and Redox:

cargo build --target=x86_64-unknown-linux-gnu
cargo build --target=x86_64-pc-windows-gnu
cargo build --target=x86_64-apple-darwin
cargo build --target=aarch64-linux-android
cargo build --target=x86_64-unknown-redox

Changelog

5

• Update dirs-sys dependency to 0.4.0.
• Add config_local_dir for non-roaming configuration on Windows. On non-Windows platforms the behavior is identical to config dir.

4

• BREAKING CHANGE The behavior of executable_dir has been adjusted to not depend on $XDG_DATA_HOME. Code, which assumed that setting the $XDG_DATA_HOME environment variable also impacted executable_dir if the $XDG_BIN_HOME environment variable was not set, requires adjustment.
• Add support for XDG_STATE_HOME.

3

• BREAKING CHANGE The behavior of the BaseDirs::config_dir and ProjectDirs::config_dir on macOS has been adjusted (thanks to everyone involved):
  • The existing config_dir functions have been changed to return the Application Support directory on macOS, as suggested by Apple documentation.
  • The behavior of the config_dir functions on non-macOS platforms has not been changed.
  • If you have used the config_dir functions to store files, it may be necessary to write code that migrates the files to the new location on macOS.
    (Alternative: change uses of the config_dir functions to uses of the preference_dir functions to retain the old behavior.)
• The newly added BaseDirs::preference_dir and ProjectDirs::preference_dir functions returns the Preferences directory on macOS now, which – according to Apple documentation – shall only be used to store .plist files using Apple-proprietary APIs. – preference_dir and config_dir behave identical on non-macOS platforms.

2

BREAKING CHANGE The behavior of deactivated, missing or invalid XDG User Dirs entries on Linux has been improved (contributed by @tmiasko, thank you!):

• Version 1 returned the user's home directory (Some($HOME)) for such faulty entries, except for a faulty XDG_DESKTOP_DIR entry which returned (Some($HOME/Desktop)).
• Version 2 returns None for such entries.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.