busybox/miscutils/mt.c

/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
//config:config MT
//config:	bool "mt (2.7 kb)"
//config:	default y
//config:	help
//config:	mt is used to control tape devices. You can use the mt utility
//config:	to advance or rewind a tape past a specified number of archive
//config:	files on the tape.

//applet:IF_MT(APPLET(mt, BB_DIR_BIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_MT) += mt.o

//usage:#define mt_trivial_usage
//usage:       "[-f DEVICE] OPCODE VALUE"
//usage:#define mt_full_usage "\n\n"
//usage:       "Control magnetic tape drive operation\n"
//usage:       "\n"
//usage:       "Opcodes:\n"
//usage:       "\n"
//usage:       "bsf bsfm bsr bss datacompression drvbuffer eof eom erase\n"
//usage:       "fsf fsfm fsr fss load lock mkpart nop offline ras1 ras2\n"
//usage:       "ras3 reset retension rewind rewoffline seek setblk setdensity\n"
//usage:       "setpart tell unload unlock weof wset"

#include "libbb.h"
#include <sys/mtio.h>

/* missing: eod/seod, stoptions, stwrthreshold, densities */
static const short opcode_value[] ALIGN2 = {
	MTBSF,
	MTBSFM,
	MTBSR,
	MTBSS,
	MTCOMPRESSION,
	MTEOM,
	MTERASE,
	MTFSF,
	MTFSFM,
	MTFSR,
	MTFSS,
	MTLOAD,
	MTLOCK,
	MTMKPART,
	MTNOP,
	MTOFFL,
	MTOFFL,
	MTRAS1,
	MTRAS2,
	MTRAS3,
	MTRESET,
	MTRETEN,
	MTREW,
	MTSEEK,
	MTSETBLK,
	MTSETDENSITY,
	MTSETDRVBUFFER,
	MTSETPART,
	MTTELL,
	MTWSM,
	MTUNLOAD,
	MTUNLOCK,
	MTWEOF,
	MTWEOF
};

static const char opcode_name[] ALIGN1 =
	"bsf"             "\0"
	"bsfm"            "\0"
	"bsr"             "\0"
	"bss"             "\0"
	"datacompression" "\0"
	"eom"             "\0"
	"erase"           "\0"
	"fsf"             "\0"
	"fsfm"            "\0"
	"fsr"             "\0"
	"fss"             "\0"
	"load"            "\0"
	"lock"            "\0"
	"mkpart"          "\0"
	"nop"             "\0"
	"offline"         "\0"
	"rewoffline"      "\0"
	"ras1"            "\0"
	"ras2"            "\0"
	"ras3"            "\0"
	"reset"           "\0"
	"retension"       "\0"
	"rewind"          "\0"
	"seek"            "\0"
	"setblk"          "\0"
	"setdensity"      "\0"
	"drvbuffer"       "\0"
	"setpart"         "\0"
	"tell"            "\0"
	"wset"            "\0"
	"unload"          "\0"
	"unlock"          "\0"
	"eof"             "\0"
	"weof"            "\0";

int mt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mt_main(int argc UNUSED_PARAM, char **argv)
{
	const char *file = "/dev/tape";
	struct mtop op;
	struct mtpos position;
	int fd, mode, idx;

	if (!argv[1]) {
		bb_show_usage();
	}

	if (strcmp(argv[1], "-f") == 0) {
		if (!argv[2] || !argv[3])
			bb_show_usage();
		file = argv[2];
		argv += 2;
	}

	idx = index_in_strings(opcode_name, argv[1]);

	if (idx < 0)
		bb_error_msg_and_die("unrecognized opcode %s", argv[1]);

	op.mt_op = opcode_value[idx];
	if (argv[2])
		op.mt_count = xatoi_positive(argv[2]);
	else
		op.mt_count = 1;  /* One, not zero, right? */

	switch (opcode_value[idx]) {
		case MTWEOF:
		case MTERASE:
		case MTWSM:
		case MTSETDRVBUFFER:
			mode = O_WRONLY;
			break;

		default:
			mode = O_RDONLY;
			break;
	}

	fd = xopen(file, mode);

	switch (opcode_value[idx]) {
		case MTTELL:
			ioctl_or_perror_and_die(fd, MTIOCPOS, &position, "%s", file);
			printf("At block %d\n", (int) position.mt_blkno);
			break;

		default:
			ioctl_or_perror_and_die(fd, MTIOCTOP, &op, "%s", file);
			break;
	}

	return EXIT_SUCCESS;
}