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#!/usr/bin/env awk -f
function log10(n) { return log(n)/log(10.0) }
function merge_meas(est_val, est_unc, meas_val, meas_unc) {
# Kalman filtering compares variances,
# convert uncertainties to square units
est_unc = (0.5*est_unc)^2.0
meas_unc = (0.5*meas_unc)^2.0
K = (est_unc)/((est_unc) + (meas_unc))
est_val = est_val + K*(meas_val - est_val)
est_unc = (est_unc*meas_unc)/(est_unc + meas_unc)
# convert est_unc back to original units
est_unc = 2.0*sqrt(est_unc)
return sprintf(OFMT OFS OFMT ORS, est_val, est_unc)
}
function sigfig(val, unc) {
ordmag_val = log10(val)
ordmag_unc = log10(unc)
#sigfig_unc = sprintf("%.f", 6)
sigfig_unc = sprintf("%.f", sqrt((ordmag_val - ordmag_unc)^2.0) + 1.0)
sigfig_val = sprintf("%.f", (ordmag_val - ordmag_unc + sigfig_unc))
ofmt_val = "%." sigfig_val "g"
ofmt_unc = "%." sigfig_unc "g"
return sprintf(ofmt_val OFS ofmt_unc ORS, val, unc)
}
function ck_boottime() {
"uname" | getline uname
close("uname")
if (uname ~/OpenBSD/) {
"sysctl kern.boottime" | getline t0_k
close("sysctl kern.boottime")
sub("^.*=", "", t0_k)
split(t0_k, t0_k_arr)
t0_k_arr[2] = (index("JanFebMarAprMayJunJulAugSepOctNovDec", t0_k_arr[2]) + 2)/3.0
gsub(":", " ", t0_k_arr[4])
t0_k = sprintf("%04d %02d %02d %s", t0_k_arr[5], t0_k_arr[2], t0_k_arr[3], t0_k_arr[4])
t0_k = mktime(t0_k)
}
return t0_k
}
function ck_uptime(t0_est, t0_unc) {
t_sys_meas[1] = systime()
t_sys_meas[2] = 1.0
"uptime" | getline t_up_cmd
close("uptime")
split(merge_meas(t_sys_meas[1], t_sys_meas[2], systime(), 1.0), t_sys_meas)
# estimate (predict) uptime
t_up_est[1] = t_sys_meas[1] - t0_est
t_up_est[2] = t_sys_meas[2] + t0_unc
# evaluate measured uptime
t_up_meas[1] = 0.0
t_up_meas[2] = systime()
sub("^.*up ", "", t_up_cmd)
sub(", load.*$", "", t_up_cmd)
split(t_up_cmd, t_up_cmd_arr, ",")
for (i in t_up_cmd_arr) {
# TODO: add cases for days, months, years, etc.
if (t_up_cmd_arr[i] ~ /day/) {
split(t_up_cmd_arr[i], days)
t_up_meas[1] += 86400.0*(days[1] + 0.0)
(t_up_meas[2] > 86400.0) ? t_up_meas[2] = 86400.0 : t_up_meas[2] += 0.0
}
if (t_up_cmd_arr[i] ~ /hr/) {
split(t_up_cmd_arr[i], hrs)
t_up_meas[1] += 3600.0*(hrs[1] + 0.0)
(t_up_meas[2] > 3600.0) ? t_up_meas[2] = 3600.0 : t_up_meas[2] += 0.0
}
if (t_up_cmd_arr[i] ~ /min/) {
split(t_up_cmd_arr[i], mins)
t_up_meas[1] += (60.0*(mins[1] + 0.0))
(t_up_meas[2] > 60.0) ? t_up_meas[2] = 60.0 : t_up_meas[2] += 0.0
}
if (t_up_cmd_arr[i] ~ /:/) {
split(t_up_cmd_arr[i], hrs_min, ":")
t_up_meas[1] += 3600.0*(hrs_min[1] + 0.0)
(t_up_meas[2] > 3600.0) ? t_up_meas[2] = 3600.0 : t_up_meas[2] += 0.0
t_up_meas[1] += 60.0*(hrs_min[2] + 0.0)
(t_up_meas[2] > 60.0) ? t_up_meas[2] = 60.0 : t_up_meas[2] += 0.0
}
}
# merge predicted and measured uptimes
split(merge_meas(t_up_est[1], t_up_est[2], t_up_meas[1], t_up_meas[2]), t_up_est)
# evaluate measured boot time, t0
t_boot_meas[1] = t_sys_meas[1] - t_up_meas[1]
t_boot_meas[2] = t_sys_meas[2] + t_up_meas[2]
# merge previous and updated boot time, t0
split(merge_meas(t0_est, t0_unc, t_boot_meas[1], t_boot_meas[2]), t_boot_est)
return sigfig(t_boot_est[1], t_boot_est[2])
}
BEGIN {
OFMT="%.21g"
pi = 4.0*atan2(1.0, 1.0)
c0 = 299792458 # m/sec
#print("_systime_", systime())
#print("_boottime_", ck_boottime())
# check ARGV for previous estimate
if (ARGC > 0) {
ARGV[1] ? t0_est[1] = ARGV[1] : t0_est[1] = ck_boottime()
ARGV[2] ? t0_est[2] = ARGV[2] : t0_est[2] = systime()
}
#print("t0_est = ", t0_est[1])
#print("t_boot_unc = ", t0_est[2])
# check uptime, update estimate
print(ck_uptime(t0_est[1], t0_est[2]))
}
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