[BK-2020-03.git] / user / bkdatediff

#!/usr/bin/env bash
# Desc: Get time difference two between date-parsable strings in seconds
# Usage: bkdatediff [STRING] [STRING]
# Example: bkdatediff "2023-01-10T08:36:42+00" "2023-01-10T12:30:13+00"
# Version 0.0.1

yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
check_depends() {
    if ! command -v date 1>/dev/random 2>&1; then die "FATAL:Missing:date"; fi;
    return 0;
}; # check dependencies
show_usage() {
    cat <<'EOF'
  USAGE:
    bkdatediff [STRING1] [STRING2]

  STRING1, STRING2
    `date` parsable strings. (i.e. variable STR in `date --date='$STR'`)

  EXAMPLE:
    bkdatediff "2023-01-10T08:36:42+00" "2023-01-10T12:30:13+00"
EOF
};
main() {
    local t1 t2;
    check_depends;
    # check args
    if [[ ! $# -eq 2 ]]; then show_usage; die "FATAL:Wrong number of args:$#"; fi;

    # get unix epoch
    t1="$(must date --date="$1" +%s)";
    t2="$(must date --date="$2" +%s)";

    # print diff in seconds
    printf "%s\n" "$((t2 - t1))";
}; # main program

main "$@";