#include "apue.h"#include <limits.h>#include <sys/resource.h>#define OPEN_MAX_GUESS	256longopen_max(void){	long openmax;	struct rlimit rl;	if ((openmax = sysconf(_SC_OPEN_MAX)) < 0 ||	  openmax == LONG_MAX) {		if (getrlimit(RLIMIT_NOFILE, &rl) < 0)			err_sys("can't get file limit");		if (rl.rlim_max == RLIM_INFINITY)			openmax = OPEN_MAX_GUESS;		else			openmax = rl.rlim_max;	}	return(openmax);}