Simple Prefix

This simple script demonstrates how to perform simple filtering and changes to the incoming record stream.

In this example, we assume that channel 4 is being filtered and we need a simple date and time prefix to each record, in the form “MM/DD HH:MM”.

function datetimeprefix(rec, chnl, tag)
 local t,s
 t = i.now
 s = string.sub(t,6,7)..“/”..string.sub(t,9,10)..“
 ”..string.sub(t,12,13)..“:”..string.sub(t,15,16)..“ ”
 mem.write(chnl,s..rec)
end

x.chnl[4].src.onrecord = datetimeprefix

The function datetimeprefix simply takes the global value i.now and splits it into the month, day, hour and minute values.
It then writes the prefix and original record to the memory channel specified (you could also use a hard-coded channel number, e.g.
mem.write(4,s..rec).

The last line “glues” the function to the event for channel 4, so that when a record arrives the ip.buffer will call the Lua function rather than storing.

Note

This functionality is easier to do with the Protocol Time Stamp field of %m/%d %H:%M