user/calcGalTick.sh

   1 #!/bin/bash
   2 # Desc: Prints a list of galactic tick dates
   3 # Usage: ./calcGalTick.sh [int start] [int end]
   4 # Input: arg1: int   start index
   5 #        arg2: int   end index
   6 # Example: ./calcGalTick.sh 0 250
   7 # Depends: bc 1.07.1; date (GNU coreutils) 8.32
   8 # Version: 0.0.1
   9 # Ref/Attrib: [1] Galactic Tick Day Calendar. (2021-10-20). https://github.com/GalacticTick/GalacticTick.github.io/blob/master/documents/press-3.pdf
  10
  11 # Galactic Tick duration equation (seconds)
  12 ## (Earth years per galactic turn) / (100ths of arcseconds per turn) * (solar days in Earth year)
  13 sGalTickEq="(225 * 10^6) / (1296000 * 100) * (365.25) * (24*3600)";
  14 #sGalTickEq="(225 * 10^6) / (1296000 * 100) * (365.24217) * (24*3600)";
  15
  16 # Galactic tick duration (seconds)
  17 sGalTick="$(echo "$sGalTickEq" | bc -l)"; # 54788453.99999999999996457600
  18 #sGalTick="$(printf "%.0f" "$sGalTick")"; # round to int
  19
  20 # Unix epoch of first tick (seconds; date Hans Lippershey patented the first telescope)
  21 ueFirstTick="$(date --date="1608-10-02" +%s)";
  22
  23 yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
  24 die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
  25 must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
  26 printGalTickDate() {
  27     # Usage: printGalTickDate [int]
  28     # Input:  arg1: nthGalTick  int  n'th observance since frist Galactic Tick
  29     #         var: sGalTick:    int   Galactic tick duration
  30     #         var: ueFirstTick: int  Unix epoch of first tick
  31     # Output: str: ISO-8601 date string
  32     # Example: printGalTickDate 239
  33     #   2023-09-09
  34     # Depends: bc 1.07.1; date (GNU coreutils) 8.32
  35     # Version: 0.0.1
  36     local nthGalTick output;
  37
  38     # Calc Unix epoch of n'th observance since first Galactic Tick
  39     ## 0th tick was first tick
  40     nthGalTick="$1";
  41     ueTickEq="( $ueFirstTick + ( ($nthGalTick - 0) * $sGalTick ) )";
  42     ueTick="$( echo "$ueTickEq" | bc -l )";
  43
  44     # Print calendar date
  45     #output="$(date --date="@$ueTick" +%Y-%m-%dT%H:%M:%S%z)";
  46     output="$(date --date="@$ueTick" +%Y-%m-%d)";
  47
  48     printf "%s\n" "$output";
  49 }; # print ISO-8601 calendar date of tick
  50 main() {
  51     start="$1";
  52     end="$2";
  53     for ((tick="$start"; tick<="$end"; tick++)); do
  54         printf "%03d: " "$tick"; # observance number
  55         printGalTickDate "$tick"; # date
  56     done;
  57 }; # main program
  58
  59 main "$@";
  60
  61 # Author: Steven Baltakatei Sandoval
  62 # License: GPLv3+