How to run scheduled scripts on linux without using cron? [closed] - linux

Question

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 5 years ago.
Improve this question
I am new to linux and shell scripting, can anyone help me create a .sh file to execute automatically every 5 hrs without using cron job

Answer 1

The right solution here is definitely cron, since it's specifically designed to handle periodic execution. If for some reason you need to avoid using it, here are some simple examples of scripts that repeatedly execute a fixed command.
Here's a naive solution that gets the job done.
#!/bin/sh
while true; do
my_command
# sleep 5 hours
sleep $((5 * 60 * 60))
done
This will run the command every five hours if the time that the command runs is negligible, since the job is run synchronously. If the command takes one hour to run, then it will be every six hours.
If you need it to run every five hours exactly, you can do the following.
This command creates a lockfile in /var/run that exists when the job is running and is deleted when the job stops. This prevents multiple instances of the job from running at the same time. The main loop will wait for five hours for my_command to finish after it's been started, and will check every 60 seconds to see if the lockfile has been removed.
#!/bin/sh
lockfile=/var/run/my_command.lock
[ -f "$lockfile" ] && {printf 'lockfile already exists\n'; exit 1;}
while true; do
if [ ! -f "$lockfile" ]; then
touch "$lockfile"
(my_command ; rm "$lockfile") &
sleep $((5 * 60 * 60))
else
printf '%s\n' "skipping! process is already running"
sleep 60
fi
done

Answer 2

You could use at command inside your script to reschedule it again after certian time.
You could put something like this at the end of your .sh script
at now +5 hours ~/myscript.sh
So every time your script finish execution it will be rescheduled to execution after 5 hours. This approach has its downsides and using cron would be the ideal way.