OSSP l2 is a C library providing a very flexible and sophisticated Unix logging facility. It is based on the model of arbitrary number of channels, stacked together in a top-down data flow tree structure with filtering channels in internal nodes and output channels on the leave nodes. Channel trees can be either constructed manually through lower-level API functions or all at once with a single API function controlled by a compact syntactical description of the channel tree. For generating log messages, a printf-style formatting engine is provided which can be extended through callback functions. The data flow inside the channel tree is controlled by logging message severity levels which are assigned to each individual channel.
