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From: witr@rwwa.com (Robert Withrow)
Newsgroups: comp.unix.bsd
Subject: Why select() returns ``exceptional'' for files?
Date: 20 Jan 1995 14:54:57 GMT
Organization: R.W. Withrow Associates
Lines: 41
Message-ID: <3fois1$5d5@shore.shore.net>
NNTP-Posting-Host: rwwa.com
The following program returns an ``exceptional'' condition
from select() for files on FreeBSD2.0 and Sunos (the two
unixoid oses I have access to...). Why?
/* This is stest.c */
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/time.h>
main()
{
fd_set readset, exceptset;
int fd;
int mask;
fd = open("./stest.c",O_RDONLY,0);
if (fd >= 0) {
int result;
int mask = 1 << fd;
struct timeval timeout;
FD_ZERO (&readset);
FD_ZERO (&exceptset);
FD_SET (fd, &readset);
FD_SET (fd, &exceptset);
timeout.tv_sec = timeout.tv_usec = 0;
result = select (8, &readset, NULL, &exceptset, &timeout);
printf("Poll got numfds=%d, readable=%d, exception=%d\n",
result,FD_ISSET(fd, &readset) != 0,FD_ISSET(fd, &exceptset) != 0);
} else printf("Can't open file\n");
exit(0);
}
-----------------------------------------------------------------------------
Robert Withrow, Tel: +1 617 598 4480, Fax: +1 617 598 4430 Net: witr@rwwa.COM
R.W. Withrow Associates, 319 Lynnway Suite 201, Lynn MA 01901 USA