A library that logs messages using non-blocking UDP datagrams.
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Making syslog() not block

liblogfaf (faf stands for fire-and-forget) is a dynamic library that is designed to be LD_PRELOAD-ed while starting a process that uses openlog() & syslog() functions to send syslog messages. It overrides logging functions to make log messages sent as UDP datagrams instead of getting written to /dev/log (which can block). This is useful for processes that call syslog() as part of their main execution flow and can therefore be easily broken when /dev/log buffer gets full, for example when the process that is expected to read from it (usually system syslog daemon like rsyslog or syslog-ng) stops doing that.

Please note that liblogfaf should not be used in an environment where reliable log message delivery is required.


liblogfaf is known to work on Linux, FreeBSD, and OS X.

Building and installing liblogfaf

  • Ensure you have libtool, autoconf, and automake installed;
  • run autoreconf -i to generate autoconf and automake files;
  • run ./configure. You can pass the '--enable-debug' option to build liblogfaf in debug mode;
  • make will build everything;
  • make install will install the library along with the logfaf script.

Using liblogfaf

The library comes with a logfaf script that can be used to start any binary with liblogfaf enabled. For example, if you run:

echo test | logfaf logger

You should see logger sending syslog UDP messages to


liblogfaf is BSD-licensed. We also provide an additional patent grant.