Messages can be attached
to maps or map items. A message consists of a time-stamp, a time interval,
a tag and a text string. Messages are only kept for a short period in memory.
Messages can also be saved
in files. Every message is prepended with the message time-stamp and the
Messages are saved in files
if two conditions are met. First, the associated item or map must have
a non-empty -path option. Second, the message tag must match one of the
patterns contained in the value of the -store option. The -store option
is a convenient way to select which messages go to a file and which not.
The file name is derived
from the value of the -path option. It is constructed from the -path value
by appending a subdirectory for the current day and the message tag as
a file name.
The message text itself is
prepended by the time-stamp (in seconds), a tab character, the time interval,
another tab character and appended to the file. New directories are created
on the fly if needed.
As an example, lets assume
we have a map where the -path option has the value /tamp/yourmap and the
-store option contains the list element “ifload*”. A message is generated
on May 27th, 1997 with the tag ifload-3 and the text “52”. This message
will be appended to the file /tmp/yourmap/1997-05-27/ifload-3.
Messages provide a convenient
mechanism to collect statistics. However, message files can consume quite
a bit of disk space. No attempts are made to compress raw message files
and there are currently no commands to read and process them later via
Tcl in a convenient way. Compression, data reduction or analysis of the
statistics should be done by specialized programs, which are run periodically.