nasin/config

config

Package config provides a configuration system for applications.

Config File Location

Config files are stored in standard operating system locations. Each application has exactly one user-level config directory within the user-level config location, and a system-level subdirectory in each of the system-level config locations (if applicable). Each subdirectory bears the application's well-known name as specified in ApplicationDescription. Each subdirectory contains a file called config.conf, which is where the actual config data is stored.

The user-level configuration file takes precendence over system configuration files, and system configuration files take precedence over eachother depending on what order they are specified in. How they are specified depends on the operating system.

Linux, Most Unixes

In terms of the XDG Base Directory Specification, an application with the well-known name com.example.Example would have its config files stored at $XDG_CONFIG_DIRS/com.example.Example/config.conf. On most systems where this specification is applicable, this will result in a file at /etc/xdg/com.example.Example/config.conf and another at $HOME/.config/com.example.Example/config.conf. The location for config files on systems that do not make use of this specification is yet to be determined.

Config File Format

The general format of the file is as follows:

• Encoded in UTF-8
• Consists of lines, separated by \n, or \r\n
• Lines can be any of these:
  • Blank line: has only whitespace
  • Comment: begins with a '#'
  • Entry: a key/value pair separated by an '=' sign

Entries

For entries, all whitespace on either side of the '=' sign, the key, or the value is ignored. The key may contain any letter or digit, as well as '-' and '.'. The value is always identified by its first rune (after the preliminary whitespace of course) and can be one of:

• String
• Number
• Bool

String

A string can be either double-quoted, or any string of runes not identifiable as any other kind of value. Quoted strings are always unquoted when they are read. Either way, these escape sequences are supported, and resolved when they are read:

• '\\': a literal backslash
• '\a': alert, bell
• '\b': backspace
• '\t': horizontal tab
• '\n': line feed
• '\v': vertical tab
• '\f': form feed
• '\r': carriage return
• '\"': double quote

Be aware that some unquoted strings, within reason, are subject to being read as some other value in the future. For example, if there were suddenly a third boolean value called glorble, the unquoted string glorble would be read as a boolean value instead of a string.

Number

A number is a floating point value. It can be of the form:

• Inf: positive infinity
• -Inf: negative infinity
• NaN: "not a number"
• [0-9]+: a whole number
• [0-9]+.[0-9]*: a fractional number

Bool

A bool is a boolean value. It can be one of:

• true
• false