Shell sleep until next full minute

terdon's suggestion would work but I guess mine is more efficient.

difference=$(($(date -d "4:00" +%s) - $(date +%s)))

if [ $difference -lt 0 ]
then
    sleep $((86400 + difference))
else
    sleep $difference
fi

This is calculating the difference between the given time and the current time in seconds. If the number is negative we have to add the seconds for a whole day (86400 to be exact) to get the seconds we have to sleep and if the number is postive we can just use it.

if the user is allowed to use at command, this is the perfect use for that:

$ at 08:00 022116
at> myscript.sh
at>      <----------- ctrl-d here
job 9 at 2016-02-21 08:00

if you get a message like "user blah is not able to run at", ask the syadmin to add this user to at.allow file or remove from at.deny file, depending on how it is used in your environment.

Unless of course you wish this days long sleep happen in the middle of your script. Even then you can cut up your script into two, writing variables you want to keep, to a file and when the time comes and second part of your script executes, it can read those variables from the stored file.