#!/usr/bin/awk -f
#
# Extract the readings of the log files for the 1st of each month, and
# add the previous' month consumption in heat and volume at the end
# of the line. The outout contains following entries:
# latest unitname, reading date, latest reading time, prev reading date,
# current total heat, prev total heat, heat diff,
# current total volume, prev total volume, volume diff
#
# the script expects the unit name set as a variable in the awk invocation
BEGIN {
    startflag=0;
};
/\/01\/.. 00:01/{
# print if there is a previous element
    if ( startflag >0 ) {
	print unitname,$1,$2,lastdate,$3+0,lastheat,$3-lastheat,$4+0,lastvol,$4-lastvol
    }
    startflag=1;
    lastheat=$3+0;
    lastvol=$4+0;
    lastdate=$1;
}