unitproc/bkdstcountdown

   1 #!/bin/bash
   2
   3 # Description: This script outputs days until the next time zone
   4 # discontinuity using 'zdump' and 'date'.
   5
   6 #=================ADJUST ME=======================
   7 SCRIPT_TZ="America/Los_Angeles" # Timezone to check for discontinuities
   8 #=================================================
   9
  10 yell() { echo "$0: $*" >&2; } # Yell, Die, Try Three-Fingered Claw technique; # Ref/Attrib: https://stackoverflow.com/a/25515370
  11 die() { yell "$*"; exit 111; }
  12 try() { "$@" || die "cannot $*"; }
  13
  14 # Declare variables
  15 declare -a datesDiscontArray #array
  16
  17 SCRIPT_YEAR=$(date +%Y)
  18 SCRIPT_YEAR_NEXT=$(( $(date +%Y) + 1))
  19 SCRIPT_YEAR_NEXT2=$(( $(date +%Y) + 2))
  20 SCRIPT_RUN_DATE_SECONDS=$(date +%s)
  21
  22 # Save zdump output for SCRIPT_YEAR (for how multiline data saved in variable, see https://stackoverflow.com/a/613580 )
  23 datesDiscont="$(zdump -c "$SCRIPT_YEAR","$SCRIPT_YEAR_NEXT2" -v $SCRIPT_TZ | grep "$SCRIPT_YEAR\|$SCRIPT_YEAR_NEXT" |  awk '{ print $2 " " $3 " " $4 " " $5 " " $6 " " $7 }'; echo)"
  24 if [ -z "$datesDiscont" ]; then
  25     echo "No time discontinuity this year.";
  26     exit 1;
  27 fi;
  28
  29 ###yell "DEBUG:datesDiscont----------";
  30 ###echo "$datesDiscont" 1>&2;
  31 ###yell "DEBUG:-----------";
  32
  33 # Count lines in datesDiscont (for counting lines in a variable, see https://stackoverflow.com/a/6314682 )
  34 #datesDiscontLineCount=$(echo "$datesDiscont" | wc -l)
  35
  36 # Convert datesDiscont into array (for how to process each line in a multiline variable, see https://superuser.com/a/284226 )
  37 while IFS= read -r line; do
  38     #echo "$line"
  39     #datesDiscontArray+="$line"
  40     datesDiscontArray+=($(date --date="$line" +%s))
  41     #echo ${datesDiscontArray[-1]}
  42 done <<< "$datesDiscont"
  43 #yell ${datesDiscontArray[@]}
  44
  45 # Sort datesDiscontArray (see https://stackoverflow.com/a/11789688 )
  46 IFS=$'\n' datesDiscontArray=($(sort <<<"${datesDiscontArray[*]}"))
  47 unset IFS
  48
  49 ###yell "DEBUG:";
  50 ###yell "DEBUG:datesDiscontArray:";
  51 ###yell "${datesDiscontArray[@]}";
  52 ###yell "DEBUG:";
  53
  54 # Get earliest date in datesDiscontArray that isn't in the past.
  55 for discontinuityDate in "${datesDiscontArray[@]}"; do
  56     ###yell "DEBUG:Discontinuity date (seconds):"$discontinuityDate
  57     ###yell "DEBUG:SCRIPT_RUN_DATE_SECONDS     :"$SCRIPT_RUN_DATE_SECONDS
  58     if [ $discontinuityDate -gt $SCRIPT_RUN_DATE_SECONDS ]; then
  59         ###yell "DEBUG:Date in future."
  60         nextDiscontDate="$discontinuityDate"
  61         break
  62     fi
  63 done
  64
  65 # Check that nextDiscontDate is not empty
  66 if [ -z "$nextDiscontDate" ]; then
  67     echo "ERROR:nextDiscontDate empty"
  68 fi;
  69
  70
  71 ###yell "DEBUG:nextDiscontDate:$nextDiscontDate";
  72 ###yell "DEBUG:SCRIPT_RUN_DATE_SECONDS:$SCRIPT_RUN_DATE_SECONDS";
  73
  74 echo $(( ( $nextDiscontDate - $SCRIPT_RUN_DATE_SECONDS )/86400 ))" days" # Days until next discontinuity date