Tape retensioning

[A. Lester Buck]

It certainly isn't very hard to do a tape manipulating program.  Here is
what I wrote several years ago to follow the man page for "mt", the SVR2
tape manipulating command.  This was for use with some tape drivers I was
moving around from system to system, so I had to be able to move the IOCTL
manipulator with me.  I left out code for checking the environment variable
TAPE and using that before the default device - feel free to add it.  And
the commands much match exactly, not just in the first unique prefix.  I
added a few synonyms for some commands, and most drivers do not support
backspace file and backspace record, so pick and choose your commands.  Mt
returns 0 exit status on success, 1 if command unrecognized, and 2 if an
operation failed.  This program requires the sys/mtio.h (or whatever) header
which defines the IOCTL's for your specific driver, but that is copyrighted
and specific for your drivers and system.  Of course, this program won't
help much if you don't have such IOCTL information.


#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/mtio.h>

#define	DEF_DEVICE	"/dev/rmt/0"

#define	FAIL	(-1)

struct	mtop	mtop = {-1, 1};

struct	entry {
	int	op;
	char	*name;
}	table[] = {
	{ MTREW,	"rewind"},
	{ MTREW,	"rew"},
	{ MTOFFL,	"offline"},
	{ MTOFFL,	"rewoffl"},
	{ MTWEOF,	"eof"},
	{ MTWEOF,	"weof"},
	{ MTFSF,	"fsf"},
	{ MTFSR,	"fsr"},
	{ MTRETEN,	"reten"},
	{ MTERASE,	"erase"},
	{ MTBSF,	"bsf"},
	{ MTBSR,	"bsr"},
	{ MTNOP,	"nop"}
};

void
usage()
{
	fprintf(stderr, "usage: mt [-f tapename] command count\n");
	exit(1);
}

main(argc, argv)
int	argc;
char	**argv;
{
	int	fd, entries, i;
	char	*devpath, *cmdname;

	if (argc < 2) {
		usage();
	}

	if (strcmp(*++argv, "-f") == 0) {
		switch (argc) {

		  case 4:
			devpath = *++argv;
			cmdname = *++argv;
			break;
		  case 5:
			devpath = *++argv;
			cmdname = *++argv;
			mtop.mt_count = atoi(*++argv);
			break;
		  default:
			usage();
		}
	} else {
		devpath = DEF_DEVICE;

		switch (argc) {

		  case 2:
			cmdname = *argv;
			break;
		  case 3:
			cmdname = *argv;
			mtop.mt_count = atoi(*++argv);
			break;
		  default:
			usage();
		}
	}

	if ((fd=open(devpath, O_RDONLY)) == FAIL) {
		fprintf(stderr, "mt: open failed on %s\n", devpath);
		exit(1);
	}

	entries = sizeof(table)/sizeof(struct entry);
	for ( i=0; i < entries; i++ ) {
		if (strcmp(table[i].name, cmdname) == 0) {
			mtop.mt_op = table[i].op;
			break;
		}
	}
	if (mtop.mt_op == -1) {
		fprintf(stderr, "mt: invalid command %s\n", cmdname);
		exit(1);
	}
	if (ioctl(fd, (int)MTIOCTOP, (caddr_t)&mtop) == FAIL) {
		perror("mt: ");
		exit(2);
	}
	exit(0);
}


-- 
A. Lester Buck     buck at siswat.lonestar.org  ...!texbell!moray!siswat!buck