style(unitproc/bktemplate):Use BEGIN/END comment markers

[BK-2020-03.git] / unitproc / bktemp-timeEpochNS

diff --git a/unitproc/bktemp-timeEpochNS b/unitproc/bktemp-timeEpochNS
index 8c0fb080273229a7c75c87ea7d7024b024482931..c490ddf1ee9170449cdbfbcdf15629a59f4a5162 100644 (file)
--- a/unitproc/bktemp-timeEpochNS
+++ b/unitproc/bktemp-timeEpochNS
@@ -1,23 +1,52 @@
 #!/bin/bash
 # Desc: Get timestamp in nanoseconds
 
+yell() { echo "$0: $*" >&2; }      #o Yell, Die, Try Three-Fingered Claw technique
+die() { yell "$*"; exit 111; }     #o Ref/Attrib: https://stackoverflow.com/a/25515370
+try() { "$@" || die "cannot $*"; } #o
 timeEpochNS() {
     # Desc: Get epoch nanoseconds
     # Usage: timeEpochNS
-    # Version 0.1.2
-    # Input: (none)
+    # Version 0.2.3
+    # Input: arg1: 'date'-parsable timestamp string (optional)
     # Output: Nanoseconds since 1970-01-01
-    # Depends: date 8
-    local currentTime epochSeconds fracNanosec epochNanosec
-    currentTime="$(date +%s.%N)";
-    epochSeconds="$(echo "$currentTime" | cut -d. -f1)";
-    fracNanosec="$(echo "$currentTime" | cut -d. -f2)";
-    epochNanosec="$(( ("$epochSeconds" * 1000000000) + ("$fracNanosec") ))";
-    echo "$epochNanosec";
+    # Depends: date 8, cut 8, yell()
+    # Ref/Attrib: Force base 10 Bash arith with '10#'. https://stackoverflow.com/a/24777667
+    local argTime timeCurrent timeInput timeEpochFloat timeEpochInt
+    local timeEpochNsFrac timeEpochNs
+
+    argTime="$1";
+
+    # Get Current Time
+    timeCurrent="$(date --iso-8601=ns)"; # Produce `date`-parsable current timestamp with resolution of 1 nanosecond.
+
+    # Decide to parse current or supplied time
+    ## Check if time argument empty
+    if [[ -z "$argTime" ]]; then
+       ## T: Time argument empty, use current time
+       timeInput="$timeCurrent";
+    else
+       ## F: Time argument exists, validate time
+       if date --date="$argTime" 1>/dev/null 2>&1; then
+           ### T: Time argument is valid; use it
+           timeInput="$argTime";
+       else
+           ### F: Time argument not valid; exit
+           yell "ERROR:Invalid time argument supplied. Exiting."; exit 1;
+       fi;
+    fi;
+    # Construct and deliver nanoseconds since 1970-01-01    
+    timeEpochFloat="$(date --date="$timeInput" +%s.%N)"; # Save ssss.NNNNNNNNN
+    timeEpochInt="$(echo "$timeEpochFloat" | cut -d. -f1)"; # Get ssss
+    timeEpochNsFrac="$(echo "$timeEpochFloat" | cut -d. -f2)"; # Get NNNNNNNNN
+    timeEpochNs="$(( (10#"$timeEpochInt" * 10**9) + (10#"$timeEpochNsFrac") ))";
+    echo "$timeEpochNs";
 } # Nanoseconds since 1970-01-01
 
 #==BEGIN sample code==
 echo "It's been $(timeEpochNS) nanoseconds since 1970-01-01.";
+echo "It's been $(timeEpochNS "10 years ago") nanoseconds since 10 years ago.";
+echo "It's been $(timeEpochNS "2003-02-01T08:59:15-05:00") nanoseconds since contact lost with STS-107.";
 #==END sample code==
 
 # Author: Steven Baltakatei Sandoval