openmax.c

unix环境高级编程一书的源码

#include	<errno.h>
#include	<limits.h>
#include	"ourhdr.h"

#ifdef	OPEN_MAX
static int	openmax = OPEN_MAX;
#else
static int	openmax = 0;
#endif

#define	OPEN_MAX_GUESS	256		/* if OPEN_MAX is indeterminate */
						/* we're not guaranteed this is adequate */
int
open_max(void)
{
	if (openmax == 0) {		/* first time through */
		errno = 0;
		if ( (openmax = sysconf(_SC_OPEN_MAX)) < 0) {
			if (errno == 0)
				openmax = OPEN_MAX_GUESS;	/* it's indeterminate */
			else
				err_sys("sysconf error for _SC_OPEN_MAX");
		}
	}
	return(openmax);
}