openmax.c

unix环境高级编程的源代码

#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);
}