How to implement polling for a function using timer in C?

naan · #1 (**permalink**) 11-11-2007

Hi,

Can you please help me in implementing a timer based polling for function in C? ie. the function should be called in say 30secs(when 30secs has lapsed).

Thanks

blowtorch · #2 (**permalink**) 11-11-2007

Use alarm(2) to set an alarm for 30 sec. When the timer runs out, a SIGALRM will be sent to your process. Catch that signal, do what you want, then set the alarm(2) again. Keep doing ad infinitum.

naan · #3 (**permalink**) 11-12-2007

Suppose if I have put the alarm in a function, and i need to catch the signal only inside the function, is it possible? ie. the process should be executing in the normal manner till it reaches this function and catches the signal.

porter · #4 (**permalink**) 11-12-2007

Quote:

Originally Posted by naan

Can you please help me in implementing a timer based polling for function in C?

The two APIs designed for this are "select" (BSD) and "poll" (SYSV).

signal driven IO (SIGIO or SIGALRM) is very rarely used and hard to get right.

Then the modern approach is using select or poll in a thread.

naan · #5 (**permalink**) 11-14-2007

Is there any apprach apart from using threads since I have not worked with threads at all.

porter · #6 (**permalink**) 11-14-2007

Depends what it's supposed to fit in.

If you are writing a program from scratch then there is no problem with

Code:

main()
{
     while (1)
     {
          sleep(30);
          doCheck();
     }
}

If it's an Xt based client application then use one of the timer callback functions.

It all depends what framework it has to work in.

naan · #7 (**permalink**) 11-18-2007

This has to be implemented in a deamon process in UNIX system. The daemon waits for any messages in a message queue and parallely has to go and execute a function by polling in every 30secs.

More UNIX and Linux Forum Topics You Might Find Helpful
Thread	Thread Starter	Forum	Replies	Last Post
Want to implement VLOOKUP (Excel function) in Unix	pravani1	Shell Programming and Scripting	8	05-26-2008 04:08 AM
Polling/Interrogate Directory Questions	dnidiffer	Shell Programming and Scripting	1	06-14-2005 09:20 PM
timer	k_oops9	Shell Programming and Scripting	3	11-08-2004 11:33 AM
how to implement timer	Frank2004	AIX	2	06-09-2004 09:21 PM
Help - Polling Script	brianmu	High Level Programming	1	09-06-2001 10:15 AM

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread: