So far, I've learned programming using languages that are interpreted (javascript.) So it's easy enough for me to draw shapes, and do cool things while the user is interacting.
But now I want to make a program that does things in the background of the users machine, and doesn't take up a lot of resources.
I'm familiar with python, so I've started making key functions, and I can run them from the terminal, but I'm lost on how I could tell the program to check for hard drives, say, every ten minutes.
Is there an OS feature that my program can get called upon every ten minutes?
Or should I do a while loop, and just wait for something to change?
The latter seems processesor-heavy, but I have no idea.
If you could just give me the keywords to Google, I could follow the rabbit hole, but this isn't something I've ever run across.
If you're on Unix, you can use cron. An example of a crontab entry that runs every ten minutes:
$ crontab -l
*/10 * * * * /home/username/script.py
Here's an intro to cron: http://www.unixgeeks.org/security/newbie/unix/cron-1.html.
On Windows, use Task Scheduler.
A very easy way to run something every 10 minutes is the following:
import time
while(True):
yourFunction(...)
time.sleep(600)
Time.sleep(600) will pause the execution of your program for 600 seconds
Related
Background
I'm struggling to find a example of WDT in the way I want to use it. Wondering if I misunderstanding its use.
my python writing is pure hobby, honestly Classes intimidate me.
in short my program reads a number of sensors connected to a raspberry pi and writes the data to a cloud hosted object database.
i have an intermittent error that while I try to figure out I want to implement a based watchdog timer.
This is what I'd like to implement so in the very least I continue to collect and store data.
I've read about the builtin watchdog timer the raspberry pi has built in here: https://diode.io/raspberry%20pi/running-forever-with-the-raspberry-pi-hardware-watchdog-20202/
The problem I want the raspberry pi to reboot if my program hangs, but when that happens the OS is still fine, so the solution in the link above is not effective.
What I'd like to implement:
set the builtin watchdog timer to reboot the raspberry pi after 200 seconds without restarting (patting?) the timer. I think the instructions for this are in the link above.
Within my python script, after I iterate through each sensor, restart (or pat?) the watchdog timer and if 200 seconds elapse between pattings (meaning my program hangs) then RPi reboots.
is this possible?
can someone help me with some simple code? I was hoping to keep this simple and avoid classes and/or threads...
thank you in advance
The WDT is probably not the right solution for the problem you are describing. Based on your description, it sounds like what you have is a program that is intended to run periodically (either on a fixed schedule or in response to some event), and that program currently has a bug that is causing it to hang intermittently and never complete it's task or terminate.
The first and best way to solve that, I'm sure you can guess, is to fix the bug. But your thinking is not unreasonable either, and doing what you describe is very common. There are many valid approaches that will do what you want without the complexity of trying to deal with a hardware timer. One of the easiest is probably to just wrap the program in a shell script and use the timeout command to limit how long it is allowed to execute before it is terminated.
Assuming the script is located at /home/user/my_script.py, and you want to run it every 10 minutes, allowing it 2 minutes before it is killed, this would work:
create a wrapper shell script:
#!/usr/bin/env bash
if ! timeout 120s python /home/user/my_script.py; then
msg="$(date) - script exceeded timeout and was killed"
else
msg="$(date) - script ran successfully"
fi
echo "${msg}" >> /home/user/my_script.log
put the script in a file, say at /home/user/wrapper_script.sh and run chmod 755 /home/user/wrapper_script.sh to make it executable.
schedule the script to run every 10 minutes using cron. At a shell, use crontab -e to edit the users crontab file and add a new line like this:
*/10 * * * * /home/user/wrapper_script.sh
now, every 10 minutes the wrapper will start automatically, and it will kick off the python script. It will wait 2 minutes for the script to stop normally, after which it will reach the timeout and terminate it.
Note: depending on how your python program is written, you might have to use some other options to the timeout command to specify which signal it should use to stop the program. If it is a very basic python script, it should be fine using the default.
Edit: based on the comments, you might be able to just change the command you're using to this:
xterm -T "HMS" -geometry 100x70+10+35 -hold -e sudo timeout 120s /usr/bin/python3 /home/pi/h$
Doing that won't actually schedule the script to run at any fixed interval, so it assumes you already have something in place to handle that. All this will do is make srue that the script is restricted to 120 seconds of run time before it is killed.
I am working on a Python program. It needs to run every 15 minutes. It currently waits 870 seconds (14.5 mins) before running again, but as the time it takes to complete the action varies, sometimes it runs before it has been 15 minutes since it last run, sometimes after 15 minutes.
My code for this part currently looks like this:
print(colour.BOLD, colour.PURPLE, "Finished", colour.END)
print(colour.BOLD, colour.BLUE, 'WAITING 15 MINUTES (900 SECONDS)', colour.END)
time.sleep(870)
Is there a way I can get it to run at xx:15, xx:30, xx:45, xx:00 where xx is every hour from 00 to 23?
Sorry if I'm being confusing here. Thanks for any help in advance.
I would use the schedule module: https://pypi.org/project/schedule/
you would run:
schedule.every().minute.at(":00").do(job)
schedule.every().minute.at(":15").do(job)
schedule.every().minute.at(":30").do(job)
schedule.every().minute.at(":45").do(job)
Use your OS tools to achieve similar results.
They are very reliable and, in case of your script failure, it will run anyway next time.
Linux
Use crontab.
How to set it will slightly change depending on your Distribution.
As a general idea:
sudo crontab -e
Inside the crontab write (be sure to customize the python executable and script path):
*/15 * * * * /usr/bin/python /path/to/your/script.py
This will make sure that your script is executed every 15 minutes.
Windows
How to schedule a task on Windows is more dependent on the Windows version you are using and it is a very visual task.
Googling "How to schedule a task in Windows" will return way better / more specific / updated results than the one I could clumsily explain here.
Here's a nice one I have found for you.
Mac
Read the amazing answer by Meki here on StackOverflow.
Having a script that does a thing at discrete intervals taking control of its own destiny like that makes me squirrely. I would use an external scheduling framework to run this job at discrete intervals. In Linux, this can be done with cronjobs; in Windows, it can be done with Task Scheduler.
Linux:
In terminal, type
crontab -e
to edit the cron schedule for the current user context. Docs on editing cron can be found all over the internet - here's one: https://www.raspberrypi.org/documentation/linux/usage/cron.md
Windows:
You can schedule a python script to run on that schedule in Windows Task Scheduler. here's a link walking through that: https://www.esri.com/arcgis-blog/products/product/analytics/scheduling-a-python-script-or-model-to-run-at-a-prescribed-time/
be certain to utilize the "if the task is already running" and "run task as soon as possible after a scheduled start is missed" options if you do this method to control appropriate behavior:
I'm trying to run a script on windows 10 machine that I set a server in my LAN.
I would like for the script to restart 30 seconds after it finished, forever.
Is there any better way then putting it in an infinite while loop?
Here is my code:
import Time
while True:
print("Here does all the things it's supposed to")
# Does something
time.wait(30)
While this works, I'm worried that it will affect performance and maybe memory of of the server or slowing it down in time.
Is there any better way to run a code forever in a loop in windows, perhaps with some command for terminal or any other option better then mine?
Kindly note the machine is a windows 10, 64 Bit arch, not a linux machine.
You can look up a term more famously known as a "chron job"
Heres an article I found out which can help: https://www.technipages.com/scheduled-task-windows
using "chron" you can schedule when to run a script at exact date and time. Or choose how to run code in infinite loop. You can also decide when to stop the script
I'm fairly competent with Python but I've never 'uploaded code' to a server before and have it run automatically.
I'm working on a project that would require some code to be running 24/7. At certain points of the day, if a criteria is met, a process is started. For example: a database may contain records of what time each user wants to receive a daily newsletter (for some subjective reason) - the code would at the right time of day send the newsletter to the correct person. But of course, all of this is running out on a Cloud server.
Any help would be appreciated - even correcting my entire formulation of the problem! If you know how to do this in any other language - please reply with your solutions!
Thanks!
Here are two approaches to this problem, both of which require shell access to the cloud server.
Write the program to handle the scheduling itself. For example, sleep and wake up every few miliseconds to perform the necessary checks. You would then transfer this file to the server using a tool like scp, login, and start it in the background using something like python myscript.py &.
Write the program to do a single run only, and use the scheduling tool cron to start it up every minute of the day.
Took a few days but I finally got a way to work this out. The most practical way to get this working is to use a VPS that runs the script. The confusing part of my code was that each user would activate the script at a different time for themselves. To do this, say at midnight, the VPS runs the python script (using scheduled tasking or something similar) and runs the script. the script would then pull times from a database and process the code at those times outlined.
Thanks for your time anyways!
I'm turning my raspberry pi running on raspbmc (based on Debian) into an alarm clock that turns my tv on, displays the weather and plays a predifined song at, you guessed it, a specific time. I currently have most of the functionality implemented with Python e.g.: storing the path to a file for the song and filling in the wake-up time via a simple web interface.
I'm wondering what the best way (least intensive) is to run the wake-up routine at a specific time entered by me and, of course, change it when a new time is entered.
Hope you guys can help me out. Thanks!
Just set up a cron task and set up a python script to perform the actions you need when triggered by cron.
Try:
% crontab -e
add a line:
10 7 * * 1-5 /path/to/your/script
Save & exit.
This should run your script at 7:10 Monday-Friday