[ILUG] [OT] C time_elapsed function

[Padraig Brady]

Colm MacCarthaigh wrote:

> On Tue, Nov 06, 2001 at 05:54:37PM +0000, Padraig Brady wrote:
> 
>>I can't beleive there isn't a platform independent
>>getSecondsSinceBoot() function, but can't find one.
>>Please tell me I'm wrong.
>>
>>
> 
> use the wtmp :)
> 
> #include <utmp.h>
> #include <strings.h>
> 
> 	time_t  	bt;
> 	struct utmp 	u;
> 	int		fd;
> 	
> 	
> 	if((fd=open("/var/run/wtmp", O_RDONLY)) < 0)
> 		/* handle error */
> 	
> 	/* set it to all zero's */
> 	bzero(bt, sizeof(bt));
> 	
> 	while(read(fd, &u, sizeof(u)) == sizeof(u))
> 	{
> 		if(u.ut_type == BOOT_TIME)
> 			bt = u.ut_time; /* ut_time is a portable macro */
> 
> 		/* dont break, we want last entry that matches */
> 	}
> 
> 	close(fd);


This just gives the boot time (in seconds since 1970) as far
as I can tell. Hence not what I want. I want the actual number
of seconds elapsed since boot, and I can't use BOOT_TIME-time(0)
as if the system date changes, this will be inaccurate.

Padraig.