Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!pasteur!ucbvax!HUMU.NOSC.MIL!kent
From: kent@HUMU.NOSC.MIL (Kent K. Kuriyama)
Newsgroups: comp.sys.apollo
Subject: Using IOCTL to control mag tape
Message-ID: <8901302320.AA10432@humu.nosc.mil>
Date: 30 Jan 89 23:20:50 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 57

I am porting a program that manipulates (e.g. rewinds) the mag 
tape unit.  It issues an IOCTL call to do this.  

------------
/*  File:  test.c  */
#include	<stdio.h>
#include	<ctype.h>

#include	<sys/ioctl.h>
#include	<sys/types.h>
#include	<sys/mtio.h>
#include	<sys/file.h>

#define tapefile  "/dev/rmt12"
main(argc, argv)
int	argc;
char	*argv[];
{
    int fd, i;
    struct	mtop	op;
	
	/* open the tape file, this seems to work */
	fd = open(tapefile, O_RDONLY);
	if (fd < 0) {
		perror(tapefile);
		exit(1);
	}

	/* rewind the tape, call to IOCTL fails */
	op.mt_op = MTREW;
	op.mt_count = 1;
	i = ioctl(fd, MTIOCTOP, &op);
	if (i < 0) {
		perror(tapefile);
		exit(1);
	}

	exit(0);
}
------------

% cc test.c
% a.out
/dev/rmt12: Not a typewriter


At run time the IOCTL call fails and I get the above message.  I 
am running Domain IX under SR9.7.1.  Could someone tell me what I 
am doing wrong?

Thanks.

Kent Kuriyama
Naval Ocean Systems Center
Hawaii Laboratory

kent@nosc.mil