alarm.awk

# alarm.awk --- set an alarm
#
# Requires getlocaltime() library function
#
# Arnold Robbins, arnold@skeeve.com, Public Domain
# May 1993
# Revised December 2010

# usage: alarm time [ "message" [ count [ delay ] ] ]

@include "gettime"

BEGIN {
    # Initial argument sanity checking
    usage1 = "usage: alarm time ['message' [count [delay]]]"
    usage2 = sprintf("\t(%s) time ::= hh:mm", ARGV[1])

    if (ARGC < 2) {
        print usage1 > "/dev/stderr"
        print usage2 > "/dev/stderr"
        exit 1
    }
    switch (ARGC) {
    case 5:
        delay = ARGV[4] + 0
        # fall through
    case 4:
        count = ARGV[3] + 0
        # fall through
    case 3:
        message = ARGV[2]
        # "break" from original code doesn't work
        # fall through
    default:
        if (ARGV[1] !~ /^[[:digit:]]{1,2}:[[:digit:]]{2}$/) {
            print usage1 > "/dev/stderr"
            print usage2 > "/dev/stderr"
            exit 1
        }
        break
    }

    # set defaults for once we reach the desired time
    if (delay == 0)
        delay = 180    # 3 minutes
    if (count == 0)
        count = 5
    if (message == "")
        message = sprintf("\aIt is now %s!\a", ARGV[1])
    else if (index(message, "\a") == 0)
        message = "\a" message "\a"
    # split up alarm time
    split(ARGV[1], atime, ":")
    hour = atime[1] + 0    # force numeric
    minute = atime[2] + 0  # force numeric

    # get current broken down time
    getlocaltime(now)

    # if time given is 12-hour hours and it's after that
    # hour, e.g., `alarm 5:30' at 9 a.m. means 5:30 p.m.,
    # then add 12 to real hour
    if (hour < 12 && now["hour"] > hour)
        hour += 12

    # set target time in seconds since midnight
    target = (hour * 60 * 60) + (minute * 60)

    # get current time in seconds since midnight
    current = (now["hour"] * 60 * 60) + \
               (now["minute"] * 60) + now["second"]

    # how long to sleep for
    naptime = target - current
    if (naptime <= 0) {
        print "alarm: time is in the past!" > "/dev/stderr"
        exit 1
    }
    # zzzzzz..... go away if interrupted
    
    if (system(sprintf("sleep %d && exit 1", naptime)) == 0)
        exit 1

    # time to notify!
    command = sprintf("sleep %d && exit 1", delay)
    for (i = 1; i <= count; i++) {
        print message
        # if sleep command interrupted, go away
        if (system(command) == 0)
            break
    }

    exit 0
}