| 1 | #!/usr/bin/env bash |
| 2 | # Description: Outputs days until next timezone discontinuity |
| 3 | # Depends: GNU Coreutils 8.32 (date), zdump 2.35, Bash 5.1.16 |
| 4 | # BK-2020-03: yell(), die(), must() |
| 5 | # Version: 0.1.0 |
| 6 | |
| 7 | # User config |
| 8 | script_tz="America/Los_Angeles"; # Timezone to check for discontinuities |
| 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 | must() { "$@" || die "cannot $*"; } |
| 13 | main() { |
| 14 | declare -a datesDiscontArray; #array |
| 15 | |
| 16 | # plumbing |
| 17 | script_year="$(date +%Y)"; |
| 18 | script_year_next="$(( script_year + 1 ))"; |
| 19 | script_year_next2="$(( script_year + 2 ))"; |
| 20 | script_run_date_seconds="$(date +%s)"; |
| 21 | |
| 22 | # Get discontinuity dates from zdump (see https://stackoverflow.com/a/613580 ) |
| 23 | datesDiscont="$(zdump -c "$script_year","$script_year_next2" -v $script_tz | \ |
| 24 | grep "$script_year\|$script_year_next" | \ |
| 25 | awk '{ print $2 " " $3 " " $4 " " $5 " " $6 " " $7 }'; echo)"; # get dates |
| 26 | if [[ -z "$datesDiscont" ]]; then |
| 27 | yell "STATUS:No time discontinuity this year."; |
| 28 | exit 1; |
| 29 | fi; |
| 30 | |
| 31 | # Convert datesDiscont into array |
| 32 | while read -r line; do |
| 33 | tunix="$(date --date="$line" +%s)"; # get unix epoch seconds |
| 34 | datesDiscontArray+=("$tunix"); |
| 35 | done < <(printf "%s\n" "$datesDiscont"); |
| 36 | |
| 37 | # Sort datesDiscontArray |
| 38 | while read -r line; do |
| 39 | datesDiscontArray+=("$line"); |
| 40 | done < <(printf "%s\n" "${datesDiscontArray[@]}" | sort); |
| 41 | |
| 42 | # # Get earliest date in datesDiscontArray that isn't in the past. |
| 43 | for discontinuityDate in "${datesDiscontArray[@]}"; do |
| 44 | if [[ $discontinuityDate -gt $script_run_date_seconds ]]; then |
| 45 | nextDiscontDate="$discontinuityDate"; |
| 46 | break; |
| 47 | fi; |
| 48 | done; |
| 49 | |
| 50 | # Check that nextDiscontDate is not empty |
| 51 | if [[ -z "$nextDiscontDate" ]]; then |
| 52 | die "FATAL:nextDiscontDate empty"; |
| 53 | fi; |
| 54 | |
| 55 | # Calculate days until next discontinuity date |
| 56 | output="$(( ( nextDiscontDate - script_run_date_seconds )/86400 )) days"; |
| 57 | printf "%s\n" "$output"; |
| 58 | |
| 59 | }; # main program |
| 60 | |
| 61 | main "$@"; |
| 62 | |
| 63 | # Author: Steven Baltakatei Sandoval |
| 64 | # License: GPLv3+ |