libeconf is a highly flexible and configurable library to parse and manage key=value configuration files. It reads configuration file snippets from different directories and builds the final configuration file for the application from it.
The first file is the vendor provided configuration file places in /usr/vendordir/project. Optionally, /run/project is also supported for ephemeral overrides.
Defining project sub directory is optional.
There are two methods of overriding this vendor settings: Copy the file from /usr/vendordir/project to /etc/project and modify the settings (see Example 1).
Alternatively, a directory named file.suffix.d/ within /etc/project can be created, with drop-in files in the form name.suffix (see Example 2).
These files contain only the changes of the specific settings the user is interested in. There can be several such drop-in files, they are processed in lexicographic order of their filename.
The first method is useful to override the complete configuration file with an own one, the vendor supplied configuration is ignored.
So, if /etc/project/example.suffix exists, /usr/vendor/project/example.suffix and /run/project/example.suffix will not be read. The disadvantage is, that changes of the vendor configuration file, due e.g. an package update, are ignored and the user has to manually merge them.
The other method will continue to use /usr/vendor/project/example.suffix as base configuration file and merge all changes from /etc/project/example.suffix.d/*.suffix. So the user will automatically get improvements of the vendor, with the drawback, that they could be incompatible with the user made changes.
If there is a file with the same name in /usr/vendor/project/example.suffix.d/ and in /etc/project/example.suffix.d/*.suffix., the file in /usr/project/vendor/example.suffix.d/ will completely ignored.
To disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/project/, with the same filename as the vendor configuration file.
Optionally, schemes with only drop-ins and without a ‘main’ configuration file will be supported too. In such schemes many drop-ins are loaded from a common directory in each hierarchy. For example, /usr/lib/.d/, /run/.d/ and /etc/.d/c.conf are all loaded and parsed in this scheme.
Example 1
If a /etc/example.suffix files exists:
- /etc/example.suffix
- /usr/vendor/project/example.suffix.d/*.suffix
- /run/project/example.suffix.d/*.suffix
- /etc/project/example.suffix.d/*.suffix
Example 2
The list of files and directories read if no /etc/example.suffix file exists:
- /usr/vendor/project/example.suffix if no /run/project/example.suffix exist
- /usr/vendor/project/example.suffix.d/*.suffix
- /run/project/example.suffix.d/*.suffix
- /etc/project/example.suffix.d/*.suffix
The libeconf library fulfills all requirements defined by the Linux Userspace API (UAPI) Group chapter "Configuration Files Specification". See: :https://uapi-group.org/specifications/specs/configuration_files_specification/
The API is written in plain C. The description can be found here :https://opensuse.github.io/libeconf/