From e9d3488a9ef1a1b5bf8e75afc719b3cce68b9853 Mon Sep 17 00:00:00 2001
From: wukong <wukong@longaeva>
Date: Sat, 22 Nov 2025 00:02:20 -0800
Subject: initial commit. ckt0.awk is launched from ckt0.sh with state stored
 in a shell variable.

---
 ckcptime.awk | 177 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 ckcptime.sh  |  21 +++++++
 ckt0.awk     | 157 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 ckt0.sh      |  38 +++++++++++++
 4 files changed, 393 insertions(+)
 create mode 100644 ckcptime.awk
 create mode 100644 ckcptime.sh
 create mode 100644 ckt0.awk
 create mode 100644 ckt0.sh

diff --git a/ckcptime.awk b/ckcptime.awk
new file mode 100644
index 0000000..4bc9539
--- /dev/null
+++ b/ckcptime.awk
@@ -0,0 +1,177 @@
+#!/usr/bin/env awk -f
+
+
+function log10(n) {
+
+    return log(n)/log(10.0)
+
+}
+
+
+function merge_meas(val_est, unc_est, val_meas, unc_meas) {
+
+    # add (meas - est) delta to the measurement uncertainty
+    # note: this works when tracking a constant value,
+    # the first derivative of a constant 'should' be zero
+    # unc_meas = sqrt(unc_meas^2.0 + (val_meas - val_est)^2.0)
+
+    # Kalman filtering compares variances
+    unc_est = (0.5*unc_est)^2.0
+    unc_meas = (0.5*unc_meas)^2.0
+
+    G_K = (unc_est)/((unc_est) + (unc_meas))
+    val_est = val_est + G_K*(val_meas - val_est)
+    unc_est = (unc_est*unc_meas)/(unc_est + unc_meas)
+
+    # convert unc_est back to same units as val_est
+    unc_est = 2.0*sqrt(unc_est)
+
+    return sprintf(OFMT OFS OFMT ORS, val_est, unc_est)
+
+}
+
+
+function sigfig(val, unc) {
+
+    ordmag_val = log10(val)
+    ordmag_unc = log10(unc)
+
+    sigfig_unc = sprintf("%.f", 6)
+    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() {
+
+    "sysctl kern.boottime" | getline t_kboot
+    close("sysctl kern.boottime")
+    sub("^.*\{", "", t_kboot)
+    sub("\}.*$", "", t_kboot)
+    split(t_kboot, t_kboot_arr, ",")
+
+    for (i in t_kboot_arr) {
+        sub("^.*= ", "", t_kboot_arr[i])
+    }
+
+    t_kboot = sprintf(t_kboot_arr[1] "." t_kboot_arr[2])
+    return t_kboot
+
+}
+
+
+function ck_cptime() {
+
+    t_sys_meas[1] = systime()
+    t_sys_meas[2] = 1.0
+
+    "sysctl kern.cp_time" | getline cptime_cmd
+    close("sysctl kern.cp_time")
+
+    split(merge_meas(t_sys_meas[1], t_sys_meas[2], systime(), 1.0), t_sys_meas)
+
+    sub("^.*=", "", cptime_cmd)
+    gsub(",", OFS, cptime_cmd)
+    #split(cptime_cmd, cptime_arr, ",")
+
+    return sprintf(OFMT OFS "%s", t_sys_meas[1], cptime_cmd)
+
+}
+
+
+function ck_uptime(t0_est, t0_unc) {
+
+    t_sys_meas[1] = systime()
+    t_sys_meas[2] = 1.0
+
+    "uptime" | getline t_up_cmd
+    close("uptime")
+
+    split(merge_meas(t_sys_meas[1], t_sys_meas[2], systime(), 1.0), t_sys_meas)
+
+    # estimate (predict) uptime
+    t_up_est[1] = t_sys_meas[1] - t0_est
+    t_up_est[2] = t_sys_meas[2] + t0_unc
+
+    # evaluate measured uptime
+    t_up_meas[1] = 0.0
+    t_up_meas[2] = systime()
+
+    sub("^.*up ", "", t_up_cmd)
+    sub(", load.*$", "", 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"
+    #print("_systime_", systime())
+    #print("_boottime_", ck_boottime())
+    printf("%s" ORS, ck_cptime())
+
+    # check ARGV for previous estimate
+    # if (ARGC > 0) {
+    #     ARGV[1] ? t0_est[1] = ARGV[1] : t0_est[1] = 0.0
+    #     ARGV[2] ? t0_est[2] = ARGV[2] : t0_est[2] = systime()
+    # }
+    #print("t0_est = ", t0_est[1])
+    #print("t_boot_unc = ", t0_est[2])
+
+    # wait (sleep) based on uncertainty
+    # print(60.0/t0_est[2])
+
+    # check uptime, update estimate
+    #print(ck_uptime(t0_est[1], t0_est[2]))
+
+}
+
diff --git a/ckcptime.sh b/ckcptime.sh
new file mode 100644
index 0000000..079faa6
--- /dev/null
+++ b/ckcptime.sh
@@ -0,0 +1,21 @@
+#!/usr/bin/env sh
+
+# estimate sytem boot time
+
+# [debug] enable execution tracing
+#set -x
+set -e
+
+# raw input data
+#date +%s
+#sysctl kern.cp_time | awk -F= '{print($0)}'
+
+#printf "sec\n" | column -t
+for N in $(seq 0 45) ; do
+    #printf "${N} ${t0_est}\n" | column -t
+    awk -f ckcptime.awk
+    sleep $( awk 'BEGIN {print( rand()^2.0 + 1.0 )}' )
+done
+
+# [debug] disable execution tracing
+set +x
diff --git a/ckt0.awk b/ckt0.awk
new file mode 100644
index 0000000..ebe724f
--- /dev/null
+++ b/ckt0.awk
@@ -0,0 +1,157 @@
+#!/usr/bin/env awk -f
+
+
+function log10(n) {
+
+    return log(n)/log(10.0)
+
+}
+
+
+function merge_meas(val_est, unc_est, val_meas, unc_meas) {
+
+    # Kalman filtering compares variances,
+    # convert uncerainties to square units
+    unc_est = (0.5*unc_est)^2.0
+    unc_meas = (0.5*unc_meas)^2.0
+
+    G_K = (unc_est)/((unc_est) + (unc_meas))
+    val_est = val_est + G_K*(val_meas - val_est)
+    unc_est = (unc_est*unc_meas)/(unc_est + unc_meas)
+
+    # convert unc_est back to original units
+    unc_est = 2.0*sqrt(unc_est)
+
+    return sprintf(OFMT OFS OFMT ORS, val_est, unc_est)
+
+}
+
+
+function sigfig(val, unc) {
+
+    ordmag_val = log10(val)
+    ordmag_unc = log10(unc)
+
+    #sigfig_unc = sprintf("%.f", 6)
+    sigfig_unc = sprintf("%.f", sqrt((ordmag_val - ordmag_unc)^2.0) + 1.0)
+    sigfig_val = sprintf("%.f", (ordmag_val - ordmag_unc + sigfig_unc))
+
+    ofmt_val = "%." sigfig_val "g"
+    ofmt_unc = "%." sigfig_unc "g"
+
+    return sprintf(ofmt_val OFS ofmt_unc ORS, val, unc)
+
+}
+
+
+# function ck_boottime() {
+# 
+#     "sysctl kern.boottime" | getline t_kboot
+#     close("sysctl kern.boottime")
+#     sub("^.*\{", "", t_kboot)
+#     sub("\}.*$", "", t_kboot)
+#     split(t_kboot, t_kboot_arr, ",")
+# 
+#     for (i in t_kboot_arr) {
+#         sub("^.*= ", "", t_kboot_arr[i])
+#     }
+# 
+#     t_kboot = sprintf(t_kboot_arr[1] "." t_kboot_arr[2])
+#     return t_kboot
+# 
+# }
+
+
+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] = 0.0
+        ARGV[2] ? t0_est[2] = ARGV[2] : t0_est[2] = systime()
+    }
+    #print("t0_est = ", t0_est[1])
+    #print("t_boot_unc = ", t0_est[2])
+
+    # wait (sleep) based on uncertainty
+    # print(60.0/t0_est[2])
+
+    # check uptime, update estimate
+    print(ck_uptime(t0_est[1], t0_est[2]))
+
+}
+
diff --git a/ckt0.sh b/ckt0.sh
new file mode 100644
index 0000000..8b9e785
--- /dev/null
+++ b/ckt0.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env sh
+
+# estimate sytem boot time
+
+# [debug] enable execution tracing
+#set -x
+set -e
+
+# raw input data
+#date +%s
+sysctl_t0_str=$( sysctl kern.boottime | mawk -F= '{print($NF)}' )
+sysctl_t0=$( date -jf "%a %b %d %H:%M:%S %G" "${sysctl_t0_str}" +%s )
+
+#epsilon1="$( mawk 'BEGIN{print(rand()^2.0)}' )"
+#t0_est="${sysctl_t0} $(date +%s)"
+#t0_est="${sysctl_t0} ${sysctl_t0}"
+#t0_est="${sysctl_t0} ${epsilon1}"
+#t0_est="${sysctl_t0} 1.0"
+
+if [ -f t0_est.log ] ; then {
+    t0_est="$( cat t0_est.log )"
+} else {
+    t0_est="${sysctl_t0} 2.0"
+} fi
+
+printf "N t0_est t0_unc\n" | column -t
+for N in $(seq 0 1440) ; do
+    printf "${N} ${t0_est}\n" | column -t
+    #t0_est=$( mawk -f ckt0.awk ${t0_est} | tail -n2 )
+    mawk -f ckt0.awk ${sysctl_t0} 2.0
+    sleep $( mawk 'BEGIN {print( rand()^2.0 + 1.0 )}' )
+    #sleep $( echo $t0_est | mawk '{print(sqrt(1.0 + ((60.0*$NF)/(60.0 + $NF))^2.0 + rand()^2.0 ))}' )
+done
+
+printf "${t0_est}\n" | tee t0_est.log
+
+# [debug] disable execution tracing
+set +x
-- 
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