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# `dirs`
*A port of the Rust `dirs` library to LFE/Erlang*
## Introduction
- a tiny low-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](https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html) and
the [XDG user directory](https://www.freedesktop.org/wiki/Software/xdg-user-dirs/) specifications on Linux and Redox
- the [Known Folder](https://msdn.microsoft.com/en-us/library/windows/desktop/dd378457.aspx) API on Windows
- the [Standard Directories](https://developer.apple.com/library/content/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/FileSystemOverview/FileSystemOverview.html#//apple_ref/doc/uid/TP40010672-CH2-SW6)
guidelines on macOS
## Platforms
This library is written in LFE but can be used transparently in Erlang or Elixir projects (that support rebar3) as if it was an Erlang library. It supports Linux, Redox, macOS and Windows.
Other platforms are also supported; they use the Linux conventions.
## Usage
Library run by user `alice` in Erlang:
```erlang
1> dirs:home();
%% Lin: /home/alice
%% Win: C:\Users\Alice
%% Mac: /Users/Alice
2> dirs:audio();
%% Lin: /home/alice/Music
%% Win: C:\Users\Alice\Music
%% Mac: /Users/Alice/Music
3> dirs:config();
%% Lin: /home/alice/.config
%% Win: C:\Users\Alice\AppData\Roaming
%% Mac: /Users/Alice/Library/Application Support
4> dirs:executable();
%% Lin: /home/alice/.local/bin
%% Win: undefined
%% Mac: undefined
```
In LFE:
```lisp
lfe> (dirs:home)
;; Lin: /home/alice
;; Win: C:\Users\Alice
;; Mac: /Users/Alice
lfe> (dirs:audio)
;; Lin: /home/alice/Music
;; Win: C:\Users\Alice\Music
;; Mac: /Users/Alice/Music
lfe> (dirs:config)
;; Lin: /home/alice/.config
;; Win: C:\Users\Alice\AppData\Roaming
;; Mac: /Users/Alice/Library/Application Support
lfe> (dirs:executable)
;; Lin: /home/alice/.local/bin
;; Win: undefined
;; Mac: undefined
```
## Design Goals
- The _dirs_ library is a low-level crate designed to provide the paths to standard directories
as defined by operating systems rules or conventions.<br/>
If your requirements are more complex, e. g. computing cache, config, etc. paths for specific
applications or projects, consider writing something higher-level that uses `dirs` -- let us know if you do, and we'll link to it!
- 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.<br/>
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.<br/>
The confusion and unexpected failure modes of such an approach would be immense.
- `executable` is specified to provide the path to a user-writable directory for binaries.<br/>
As such a directory only commonly exists on Linux, it returns `undefined` on macOS and Windows.
- `font` is specified to provide the path to a user-writable directory for fonts.<br/>
As such a directory only exists on Linux and macOS, it returns `undefined` on Windows.
- `runtime` 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.<br/>
As such a directory only commonly exists on Linux, it returns `undefined` on macOS and Windows.
## Features
| Function name | Value on Linux/Redox | Value on Windows | Value on macOS |
|--------------------| ---------------------------------------------------------------------- |-----------------------------------| ------------------------------------------- |
| `dirs:home` | `$HOME` | `{FOLDERID_Profile}` | `$HOME` |
| `dirs:cache` | `$XDG_CACHE_HOME` or `$HOME/.cache` | `{FOLDERID_LocalAppData}` | `$HOME/Library/Caches` |
| `dirs:config` | `$XDG_CONFIG_HOME` or `$HOME/.config` | `{FOLDERID_RoamingAppData}` | `$HOME/Library/Application Support` |
| `dirs:config_local` and `dirs:config-local`| `$XDG_CONFIG_HOME` or `$HOME/.config` | `{FOLDERID_LocalAppData}` | `$HOME/Library/Application Support` |
| `dirs:data` | `$XDG_DATA_HOME` or `$HOME/.local/share` | `{FOLDERID_RoamingAppData}` | `$HOME/Library/Application Support` |
| `dirs:data_local` and `dirs::data-local` | `$XDG_DATA_HOME` or `$HOME/.local/share` | `{FOLDERID_LocalAppData}` | `$HOME/Library/Application Support` |
| `dirs:executable` | `$XDG_BIN_HOME` or `$HOME/.local/bin` | `undefined` | `undefined` |
| `dirs:preference` | `$XDG_CONFIG_HOME` or `$HOME/.config` | `{FOLDERID_RoamingAppData}` | `$HOME/Library/Preferences` |
| `dirs:runtime` | `$XDG_RUNTIME_DIR` or `undefined` | `undefined` | `undefined` |
| `dirs:state` | `$XDG_STATE_HOME` or `$HOME/.local/state` | `undefined` | `undefined` |
| `dirs:audio` | `XDG_MUSIC_DIR` or `undefined` | `{FOLDERID_Music}` | `$HOME/Music` |
| `dirs:desktop` | `XDG_DESKTOP_DIR` or `undefined` | `{FOLDERID_Desktop}` | `$HOME/Desktop` |
| `dirs:document` | `XDG_DOCUMENTS_DIR` or `undefined` | `{FOLDERID_Documents}` | `$HOME/Documents` |
| `dirs:download` | `XDG_DOWNLOAD_DIR` or `undefined` | `{FOLDERID_Downloads}` | `$HOME/Downloads` |
| `dirs:font` | `$XDG_DATA_HOME/fonts` or `$HOME/.local/share/fonts` | `undefined` | `$HOME/Library/Fonts` |
| `dirs:picture` | `XDG_PICTURES_DIR` or `undefined` | `{FOLDERID_Pictures}` | `$HOME/Pictures` |
| `dirs:public` | `XDG_PUBLICSHARE_DIR` or `undefined` | `{FOLDERID_Public}` | `$HOME/Public` |
| `dirs:template` | `XDG_TEMPLATES_DIR` or `undefined` | `{FOLDERID_Templates}` | `undefined` |
| `dirs:video` | `XDG_VIDEOS_DIR` or `undefined` | `{FOLDERID_Videos}` | `$HOME/Movies` |
## License
Apache License, Version 2.0
Copyright © 2023, Duncan McGreggor <oubiwann@gmail.com>.
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