Logger - yet an other Variable Logging Utility

The Logger (logger.c)

The logger is a utility to write the history of object parameters. For all drivers based on pardef it is automatically switched on. The data is logged typically every 5 seconds to a file, but only changes are stored in order to save disk space. The file specification for the logfiles is:

<logger base path>/<variable name>/MM-DD.log

Files older than one year will be overwritten. The variable name is the object name for the basic value of the object or <object name>.<parameter name> for the parameters. Important parameter names might be configured to have a more descriptive name.

Syntax of the Log Files

First there is a header line, containing the date and some additional information:

isdst

0/1 when daylight saving time is in effect or not

period

the minimal interval between logged values

exact

0: plot points should be connected with a straight line, 1: plot curves should have only horizontal and vertical lines

For every logger entry, there is one line, containing the time, a tab as separation and a value, (which may be a text or number). There may also be lines starting with a hash symbol, which may contain the same information as in the header line, or just a comment.

#2005-10-30 00:00:00 isdst 1 period 5 exact 0
00:00:00        100.72
00:00:05        100.73
00:01:10        100.73
00:01:15        100.74
00:01:20        100.73

      ...                                   many lines omitted

02:59:55        100.56
#isdst 0                                    change of daylight saving time
02:00:00        100.58

      ...                                   many lines omitted

07:55:00        100.58                      the server was shut down after writing this line
#period 5 exact 0 isdst 0                   the server restarts at 8:30
07:55:05                                    the shutdown time and an empty value
08:30:00        99.95                       the first logged value after startup

The Log Reader (logreader.c)

There is also a utility to read the logged data through the SICS server.