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/*++
/* NAME
/* fifo_rdwr_bug 1
/* SUMMARY
/* fifo server test program
/* SYNOPSIS
/* fifo_rdwr_bug
/* DESCRIPTION
/* fifo_rdwr_bug creates a FIFO and opens it read-write mode.
/* On BSD/OS 3.1 select() will report that the FIFO is readable
/* even before any data is written to it. Doing an actual read
/* causes the read to block; a non-blocking read fails.
/* DIAGNOSTICS
/* Problems are reported to the standard error stream.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
#include <sys_defs.h>
#include <sys/time.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#define FIFO_PATH "test-fifo"
#define perrorexit(s) { perror(s); exit(1); }
static void cleanup(void)
{
printf("Removing fifo %s...\n", FIFO_PATH);
if (unlink(FIFO_PATH))
perrorexit("unlink");
printf("Done.\n");
}
int main(int unused_argc, char **unused_argv)
{
struct timeval tv;
fd_set read_fds;
fd_set except_fds;
int fd;
(void) unlink(FIFO_PATH);
printf("Creating fifo %s...\n", FIFO_PATH);
if (mkfifo(FIFO_PATH, 0600) < 0)
perrorexit("mkfifo");
printf("Opening fifo %s, read-write mode...\n", FIFO_PATH);
if ((fd = open(FIFO_PATH, O_RDWR, 0)) < 0) {
perror("open");
cleanup();
exit(1);
}
printf("Selecting the fifo for readability...\n");
FD_ZERO(&read_fds);
FD_SET(fd, &read_fds);
FD_ZERO(&except_fds);
FD_SET(fd, &except_fds);
tv.tv_sec = 1;
tv.tv_usec = 0;
switch (select(fd + 1, &read_fds, (fd_set *) 0, &except_fds, &tv)) {
case -1:
perrorexit("select");
default:
if (FD_ISSET(fd, &read_fds)) {
printf("Opening a fifo read-write makes it readable!!\n");
break;
}
case 0:
printf("The fifo is not readable, as it should be.\n");
break;
}
cleanup();
exit(0);
}
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