Any similar function as Arduino's delay() in Linux C program?

brownlinux · 10-11-2020, 02:06 PM

Hi, I am writing C program under Linux. Is there a builtin function that allows me to use something like the delay() function in Arduino?

https://www.arduino.cc/reference/en/...ns/time/delay/

sgosnell · 10-11-2020, 02:55 PM

C is C, pretty much. The OS is immaterial.

berndbausch · 10-11-2020, 03:56 PM

There is usleep.

Since your program is not alone on a Linux system, you need to be aware that the sleep time is not that accurate:

Quote:

The sleep may be lengthened slightly by any system activity

brownlinux · 10-11-2020, 04:33 PM

Quote:

Originally Posted by berndbausch

There is usleep.

Since your program is not alone on a Linux system, you need to be aware that the sleep time is not that accurate:

In general, how much off will that be? Less than a second, 500ms, 10ms, 1ms? Are there ways to achieve more accurate results? For example, getting some kind of stopwatch...

Will keep pulling the time (e.g. date command on linux. not sure about C's function to access it) and checking the difference to see if x msec has passed work better?

berndbausch · 10-11-2020, 05:08 PM

Quote:

Originally Posted by brownlinux

In general, how much off will that be? Less than a second, 500ms, 10ms, 1ms? Are there ways to achieve more accurate results? For example, getting some kind of stopwatch...

This depends on factors like CPU speed, number of CPUs, system load etc. I don't think a general statement can be made. See also https://www.linuxquestions.org/quest...ep-4175682641/.

Quote:

Will keep pulling the time (e.g. date command on linux. not sure about C's function to access it) and checking the difference to see if x msec has passed work better?

You could use gettimeofday as in the above link. It's worth a try, but you should also explore realtime priorities to mitigate the above factors.

brownlinux · 10-11-2020, 06:35 PM

Quote:

Originally Posted by berndbausch

This depends on factors like CPU speed, number of CPUs, system load etc. I don't think a general statement can be made. See also https://www.linuxquestions.org/quest...ep-4175682641/.

You could use gettimeofday as in the above link. It's worth a try, but you should also explore realtime priorities to mitigate the above factors.

Thank you. What are realtime priorities and how to explore them?

berndbausch · 10-11-2020, 07:14 PM

Realtime priorities allow a process to gain access to the CPU as soon as it wants it, rather than waiting in a run queue.

I can't tell you how to use them, but there should be plenty of information about them on the internet.