n line sum: h:mm; average: h:mm:ss

#!/bin/bash
# Set script related variables:
# Input and output files:
input="/home/uplog.txt"			# Input log file (this file will be
					# updated in place if it contains more
					# than "maxrec" records).
output_averages="/home/averages.txt"	# Output averages file.

# Record counts:
maxrec=200				# Maximum # of lines to keep in log file.
nl_av1=7				# # of lines to be used for 1st average.
nl_av2=30				# # of lines to be used for 2nd average.
# Time and date stuff:
read V R <<-EOF
	$(date '+%x %A  %d/%m/%y die %V.week')
EOF
T=$((86400/3600))			# Hours in a day (the hard way)

# Data for log entry:
machine=$(uname -n)			# Node name.

# Get time since reboot from uptime:
IFS=' ,' read junk junk H_or_HM junk <<-EOF
	$(uptime)
EOF

echo $T "not yet"			# ???
echo $USER				# shows me the actual user
echo "today is" $R 

# Add entry to log file:
echo "uptime $USER an $machine   $H_or_HM   $V" >> "$input"

# Process log file:
awk -v maxrec="$maxrec" -v nl_av1="$nl_av1" -v nl_av2="$nl_av2"  \
	-v avoutf="$output_averages" '
# Normalize script variables:
BEGIN {	# Do not accept averages for more lines than we are saving...
	# Do not average more input lines than we are keeping in the output.
	if(nl_av1 > maxrec) {
		printf("nl_av1 reduced from %d to %d.\n", nl_av1, maxrec)
		nl_av1 = maxrec
	}
	if(nl_av2 > maxrec) {
		printf("nl_av2 reduced from %d to %d.\n", nl_av2, maxrec)
		nl_av2 = maxrec
	}
	# Set size of uptime data circular buffer:
	m = nl_av1 > nl_av2 ? nl_av1 : nl_av2
}
# Save input file pathname in case we need to trim it to maxrec lines.
NR == 1 {
	inf = FILENAME
}
# Process input log file data:
{	# Save last maxrec lines in input circular buffer (l[]):
	l[NR % maxrec] = $0
	# Convert uptime "x mins," or "hours:minutes," to minutes and save it in
	# another circular buffer (mins[]).
	nf = split($5, hm, /[:,]/)
	if (nf == 1) {
		# We just have minutes.
		mins[NR % m] = hm[1]
	} else {# We have hours and minutes separated by a ":".
		mins[NR % m] = hm[1] * 60 + hm[2]
	}
	printf("mins[%d] = %d from %s\n", NR % m, mins[NR % m], $5)
}
# Function to calculate sum and average uptime from last "n" entries in the
# mins[] circular buffer.
# Returns number of lines actually used in calculations.
function av(n,		i) {
	if(n > NR) {
		# Calculate sum and average based on all saved lines.
		n = NR
	}
	t = 0
	for(i = NR - n + 1; i <= NR; i++)
		t += mins[i % m]
	a = t / n
	# printf("av(%d): total=%d minutes, average=%.2f minutes\n", n, t, a)
	return n
}
# Function to convert "m" minutes to "H" hours, "M" minutes, and "S" seconds.
function m2hms(m) {
	S = (m % 1) * 60		# seconds
	M = int(m % 60)			# minutes
	H = int(m / 60)			# hours
}
# We have hit EOF on input, rewrite input file if we found more than "maxrec"
# lines, calculate and print both sums and averages.
END {	# If we had more than "maxrec" input lines, trim input file to "maxrec"
	# lines.
	if(NR > maxrec) {
		for(i = NR - maxrec + 1; i <= NR; i++)
			print l[i % maxrec] > inf
		printf("Input file %s trimmed from %d lines to %d lines\n",
			inf, NR, maxrec)
	} else	printf("Input file %s: %d lines processed.\n", inf, NR)
	# Print averages.
	L = av(nl_av1)
	m2hms(t)
	printf("%d line sum: %d:%02d; ", L, H, M) > avoutf
	m2hms(a)
	printf("average: %d:%02d:%02.0f\n", H, M, S) > avoutf
	L = av(nl_av2)
	m2hms(t)
	printf("%d line sum: %d:%02d; ", L, H, M) > avoutf
	m2hms(a)
	printf("average: %d:%02d:%02.0f\n", H, M, S) > avoutf
}' "$input"