Log Message:
Import ossp-l2-0.9.13 as wip/ossp-l2.

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
(eight fixed and nine custom) logging message severity levels which are assigned
to each individual channel.

Channels are implemented by channel handlers which can be even customer supplied
for creating own channels which seamlessly integrate into the framework. For
convenience reasons, OSSP l2 already ships with pre-implemented filtering (noop,
filter, prefix, buffer) and output (null, fd, file, pipe, socket, syslog, smtp)
channels which already cover mostly all use cases of logging.