storing variable value

[Daniel Dalton]

Hi!

I'm writing a program to provide me with battery warnings when my
battery hits certain levels. It just checks the current level and does
something. I plan to call it from a a cron job. But If the cron runs
every minute, warnings every minute would be rather annoying. so is
there a way to make the script check if it has already ran before?
eg. can I write to a variable on one run of the program, and on the next
read that value that was written?

Thx!

Daniel.


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[Diez B. Roggisch]

Hi!

I'm writing a program to provide me with battery warnings when my
battery hits certain levels. It just checks the current level and does
something. I plan to call it from a a cron job. But If the cron runs
every minute, warnings every minute would be rather annoying. so is
there a way to make the script check if it has already ran before?
eg. can I write to a variable on one run of the program, and on the next
read that value that was written?

Use a file to store previous run's state. Use e.g. the pickle-module to
store some arbitrary data-structures to the disk.


Diez

 

[Steven D'Aprano]

Hi!

I'm writing a program to provide me with battery warnings when my
battery hits certain levels. It just checks the current level and does
something. I plan to call it from a a cron job. But If the cron runs
every minute, warnings every minute would be rather annoying. so is
there a way to make the script check if it has already ran before? eg.
can I write to a variable on one run of the program, and on the next
read that value that was written?

No, every time cron calls your script, it calls it as new. If you want
persistent storage, you need to write to persistent storage like a file.

Another solution is to use a daemon which is running continuously in the
background. Because that's a long-running process, the daemon can then
decide how often it checks the battery, and how often it notifies you.
However, writing correct daemons is not something for a beginner. I
recommend you just stick to writing your persistent data to a file
somewhere, and sticking to cron.