Good method to compare time?

Question

I need to check for the current time and abort the script if it is not proper time of day I am supposed to run it. Also, if anyone else runs it, it should abort.

For example: I need my script to only run if it is started between 10 PM and and 2 AM (a 4 hour window).

Currently I am doing the following. Taking the time with date +%k%M and comparing with hard coded numbers

#!/bin/sh
currTime=`date +%k%M`
check_time_to_run()
{
    tempTime=$1
    if [ $tempTime -gt 200 -a $tempTime -lt 2200 ]; then 
        echo "Time is between 2 AM and 10 PM. Aborting."
        exit 1
    else
        echo "Time is after 10 PM and before 2 AM. Running normally."
    fi
}

check_time_to_run $currentTime

I would like to know if there is any other efficient method with respect to time comparision in sh or bash ?

Answer 1

That looks perfect to me. What makes you think it should be improved?

Anyway, ways to improve it could be:

• Use a smaller, quicker shell than bash like dash or pdksh.
• use a shell that has date capabilities builtin like zsh or ksh93
• use gawk (which is smaller than bash, but not than dash but could avoid the extra fork):

Example:

#! /usr/bin/gawk -f
BEGIN {now = strftime("%k%M")+0; exit(now > 200 && now < 2200)}

Answer 2

If external tools are allowed you might want to check dateutils.

Your "script'' becomes:

if dtest time --gt '02:00:00' && dtest time --lt '22:00:00'; then
    echo "Time is between 2 AM and 10 PM. Aborting."
fi

Disclaimer: I am the author of said tool.