Why the shell can't be exectuted ?

luofeiyu · 12-21-2015, 10:00 PM

I edit the file as /home/keep_eye.sh.

Code:

sleep 3600
sync
echo -n "if you want to close computer ,please input y"
read closeit
if [ $closeit = 'y']
then
    shutdown -h now
else
    echo "continue"
fi

The computer will be shutdown every 60 miniutes at my willing.
The shell was crontabed with command

Code:

    crontab -e 
    @reboot  sh /home/keep_eye.sh

It will not be executed ,why ?

NevemTeve · 12-21-2015, 10:55 PM

When running from crontab, the standard input of the script is directed to /dev/null, so 'read' will never get 'y' from there.

luofeiyu · 12-21-2015, 11:03 PM

The three lines code here

Code:

sleep 3600
sync
shutdown -h now

can protect my eye for every hour to shutdown my pc when to set in crontab,but sometimes i have an important work to do ,i have to work continuously.
How to solve the problem then?

rtmistler · 12-22-2015, 07:05 AM

Unclear, you claim that you wish to force a shutdown once per hour to alleviate eyestrain. Therefore why allow an option to cancel it? However I do understand that people ultimately will wish to have that option.

Run the cron job to shutdown once per hour, but how about sleep for 3300 and then use wall(1) to send a message to all terminals stating that the system will be shut down in 5 minutes and alert them to cancel, or restart the cron job if they wish to delay the process. Then sleep another 300 and finally shutdown if the cron wasn't restarted.

rknichols · 12-22-2015, 10:06 AM

Wouldn't a "typing break" applet accomplish the same thing? Many Linux distros include one by default, or you can do a web search for "linux typing break" (without the quotes) for some alternatives.

Ramurd · 12-24-2015, 08:02 AM

another approach is, instead of it reading from terminal (which is not available in the cron), let it check for the existence of a certain file in, say, /tmp.
It's not safe at all; but then again... there are flaws already pointed out.

Code:

sleep 3600
sync
if [[ ! -e /tmp/noshutdown ]]
then
    wall "Shutting down in a few seconds, please save your work."
    shutdown -h 10
else
    wall "Not shutting down, the file /tmp/noshutdown exists."
fi

Myself, I would find such a script highly annoying... but that's me I suppose.
You could also, instead of shutting down the system, force the screen to turn off / on, when using X:

to turn it off:

Code:

xset dpms force off

bigearsbilly · 01-04-2016, 02:33 AM

get a raspberry pi and use the GPIO pins to periodically switch a relay which
pumps 240v AC into your keyboard, forcing you to stop/die.