How can uptime be used to trigger an action?

Question

I want to write shell or perl code which would give me notification after x days. Basically on SUSE Linux server, there is reboot required after 208 days, else the system would freeze. This is known bug. So in order to avoid this, I want notification mail coming to me before 8 days something like that....just an alert..

The script has to check the current uptime and then calculate the remaining days required for total 208 days. Hope this makes sense.

Answer 1

You can easily determine the uptime in days with awk:

# Print days of uptime, or zero if less than 1 day.
uptime | awk '/days?/ {print $3; next}; {print 0}'

You can use this with command substitution to perform any action you like based on the results. For example:

#!/bin/bash
days () { uptime | awk '/days?/ {print $3; next}; {print 0}'; }
UPTIME_THRESHOLD=200
if [ $(days) -ge $UPTIME_THRESHOLD ]; then
    : # Take some action.
fi

Obviously, the action you take is up to you. You can mail yourself messages, schedule a reboot with the at command, or anything else that you feel necessary to do.

You may also wish to set this script up as a daily cron job, so that it will trigger your defined action when the uptime threshold has been exceeded. If you have root access, you could simply drop the script into /etc/cron.daily/, or you might set up your personal crontab to call this script once a day.

Answer 2

Inspired by CodeGnome answer, made a small script for mac, where a notification shows up after the computer is on for 8:30. Also had to configure cron to run this every minute.

#!/bin/bash
timeup () { uptime | awk  '{print $3}'; }
UPTIME="8:30,"
if [ $(timeup) == $UPTIME ]; then
    osascript -e 'tell app "Finder" to display dialog "8:30 uptime! Go Home!"' &
    osascript -e 'display notification "8:30 uptime! Go Home!" with title "Go Home!!"' &
fi