The following example selects every available information about the log message, except for the date-related macros (R_* and S_*), selects the .SDATA.meta.sequenceId macro, and defines a new value-pair called MSGHDR that contains the program name and PID of the application that sent the log message.

$(format-json --scope syslog,all_macros,selected_macros \
  --exclude R_* --exclude S_* --key .SDATA.meta.sequenceId \
  --pair MSGHDR="$PROGRAM[$PID]: ")

The following example shows how to use this template function to store log messages in JSON format:

destination d_json {
  file("/var/log/messages.json" template("$(format_json --scope selected_macros --scope nv_pairs)"));
};