michaelgalassi / liblog Goto Github PK

Liblog is a very fast low-overhead logger targeted at developers.
It is not meant for customer use.

Liblog is a tiny daemon which maintains a small shared memory segment
to which your application writes it's messages.  When you need a copy
of the messages you need but run "killall -USR1 lldump" and the shared
memory segment will be written to disk.  New messages overwrite old
ones when the log buffer fills up.  The messages can then be extracted
with the llcat utility.

The interface is very simple.  Logging is initiated with a call to
ll_open(), there are two arguments, the minimum logging level and the
size of the shared memory buffer.  Log levels are defined in liblog.h.
ll_open creates the shared memory segment and starts the daemon.  It
returns 0 on success, -1 on failure.  One writes to the log with calls
to ll_log(), the arguments are the level, a printf style format
string, and a variable number of arguments.  When you're done you
terminate logging with ll_close() which flushes the buffer to disk and
frees the shared memory segment.

Because the shared memory segment has a header in front of your
messages and the messages are not necessarily in order a small utility
is provided to examine the messages, it is called llcat and it takes
one argument, the name of the logfile to be displayed.

It's usage might look something like this:

#include <liblog.h>
int
main(int argc, char **argv)
{
   if (debug) {
      /* log warnings and above, keep last 16k */
      if (ll_open(LL_LVL_WARN, 16*1024) == -1) {
         (void)fprintf(stderr, "failed to open liblog\n");
         return 1;
      }
   }
   ...
   /* log anything above debug */
   (void)ll_setlevel(LL_LVL_DBG);
   if (debug) {
      ll_log(LL_LVL_NOTE, "i: %d str: %s\n, i, s);
   }
   ...
   /* this also flushes to disk */
   ll_close();
   return 0;
}