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Application Programming Interface
---------------------------------
The EventLog library implements a set of functions to construct, format and
output event records.
The public symbols are defined in the header file named <evtlog.h>, for a
list and documentation of functions please consult that file as it contains
inline function descriptions in gtk-doc format.
It is very important to use consistent tag naming and that different
applications use identify the same data with the same tag name. Therefore
please use the predefined tag name if one is available. Predefined tag names
are defined in the header file <evtmaps.h>. This header is included by
<evtlog.h> therefore you will not need to reference it explicitly.
A third header file named "evt_internals.h" is defines the internals of the
EventLog library. Please do not depend on its contents and don't include it
directly. As this header file is not meant to be used in applications, it is
not installed when the library is installed.
Syslog compatibility
--------------------
Most UNIX systems and therefore the programs running under UNIX use the
syslog() API found in the libc for logging. Because of the large installed
base it is worth supporting legacy applications before they are converted to
use EventLog.
Two different implementations of syslog compatibility is provided: macro and
linker based.
* Macro based compatibility
This works by defining the syslog() function names as macros to refer to
the compatibility functions found in EventLog. To use the macro based
wrapper you will need to recompile the program from source:
$ cc -DEVENTLOG_SYSLOG_MACROS syslogapp.c -levtlog
* Linker based compatibility
Some dynamic linker implementations (most notably: Linux and Solaris)
support symbol overloading. EventLog can use this feature if the dlsym()
function is present which supports RTLD_NEXT to fetch symbols hidden by
EventLog itself.
To enable this wrapper configure EventLog with the --enable-dlsym-wrapper
configure option. To use the wrapper you simply need to preload the
event log shared object like:
$ LD_PRELOAD=/usr/lib/libeventlog.so.0 syslogapp
Where syslogapp is the program to be run. As you can see the application
itself did not need to be recompiled.
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