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Annotation of cci/usr/src/man/man4/mt.4, revision 1.1

1.1     ! root        1: .TH MT 4 4/1/81
        !             2: .SH NAME
        !             3: mt \- UNIX magtape interface
        !             4: .SH DESCRIPTION
        !             5: The files
        !             6: .I "cy0s, ..., cy15s"
        !             7: refer to the UNIX magtape drives,
        !             8: which may be on the VERSABUS using the CIPHER tapemaster formatter
        !             9: .IR cy (4),
        !            10: The following description applies to any of the transport/controller pairs.
        !            11: The files
        !            12: .I "cy0s, ..., cy15s"
        !            13: are read/written in 25ips, 
        !            14: The density (1600 bpi or 3200 bpi) is selected by a switch on the drive.
        !            15: The files
        !            16: .I "cy0s, ..., cy7s"
        !            17: are rewound when closed.
        !            18: The non-rewinding files are named
        !            19: .I ncy[0-7]
        !            20: respectively.
        !            21: .PP
        !            22: For compatibility, the
        !            23: .I [n]cy*s
        !            24: files are linked to appropriate
        !            25: .I [n]mt*
        !            26: files.
        !            27: .PP
        !            28: When a file open for writing is closed, two file-marks are written.
        !            29: If the tape is not to be rewound
        !            30: it is positioned with the head between the two
        !            31: file-marks.
        !            32: .PP
        !            33: A standard tape consists of a
        !            34: series of 1024 byte records terminated by two
        !            35: file-marks.
        !            36: To the extent possible, the system makes
        !            37: it possible, if inefficient, to treat
        !            38: the tape like any other file.
        !            39: Seeks have their usual meaning and it is possible
        !            40: to read or write a byte at a time.
        !            41: .PP
        !            42: The
        !            43: .I mt
        !            44: files discussed above are useful
        !            45: when it is desired to access the tape in a way
        !            46: compatible with ordinary files.
        !            47: When foreign tapes are to be dealt with, and especially
        !            48: when long records are to be read or written, the
        !            49: `raw' interface is appropriate.
        !            50: Writing in very small units is inadvisable,
        !            51: however, because it tends to create monstrous record
        !            52: gaps.  The associated files are named
        !            53: .I "rcy0s, ..., rcy15s,"
        !            54: but the same minor-device considerations as for the regular files still apply,
        !            55: as well as the appropriate
        !            56: .I r[n]mt*
        !            57: links.
        !            58: .PP
        !            59: A number of other ioctl operations are available
        !            60: on raw magnetic tape.
        !            61: The following definitions are from <sys/mtio.h>:
        !            62: .PP
        !            63: .nf
        !            64: /*
        !            65:  * Structures and definitions for mag tape io control commands
        !            66:  */
        !            67: 
        !            68: /* mag tape io control commands */
        !            69: #define MTIOCTOP       (('m'<<8)|1)    /* do a mag tape op */
        !            70: #define MTIOCGET       (('m'<<8)|2)    /* get mag tape status */
        !            71: 
        !            72: /* structure for MTIOCTOP - mag tape op command */
        !            73: struct mtop    {
        !            74:        short   mt_op;          /* operations defined below */
        !            75:        daddr_t mt_count;       /* how many of them */
        !            76: };
        !            77: 
        !            78: /* operations */
        !            79: #define MTWEOF 0       /* write an end-of-file record */
        !            80: #define MTFSF  1       /* forward space file */
        !            81: #define MTBSF  2       /* backward space file */
        !            82: #define MTFSR  3       /* forward space record */
        !            83: #define MTBSR  4       /* backward space record */
        !            84: #define MTREW  5       /* rewind */
        !            85: #define MTOFFL 6       /* rewind and put the drive offline */
        !            86: #define MTNOP  7       /* no operation, sets status only */
        !            87: 
        !            88: /* structure for MTIOCGET - mag tape get status command */
        !            89: 
        !            90: struct mtget   {
        !            91:        short   mt_type;                /* type of magtape device */
        !            92: /* the following two registers are grossly device dependent */
        !            93:        short   mt_dsreg;               /* ``drive status'' register */
        !            94:        short   mt_erreg;               /* ``error'' register */
        !            95: /* end device-dependent registers */
        !            96:        short   mt_resid;               /* residual count */
        !            97: /* the following two are not yet implemented */
        !            98:        daddr_t mt_fileno;      /* file number of current position */
        !            99:        daddr_t mt_blkno;       /* block number of current position */
        !           100: /* end not yet implemented */
        !           101: };
        !           102: 
        !           103: /*
        !           104:  * Constants for mt_type byte
        !           105:  */
        !           106: #define MT_ISTS                01
        !           107: #define MT_ISHT                02
        !           108: #define MT_ISTM                03
        !           109: .fi
        !           110: .ft R
        !           111: .PP
        !           112: Each
        !           113: .I read
        !           114: or
        !           115: .I write
        !           116: call reads or writes the next record on the tape.
        !           117: In the write case the record has the same length as the
        !           118: buffer given.
        !           119: During a read, the record size is passed
        !           120: back as the number of bytes read, provided it is no greater
        !           121: than the buffer size;
        !           122: if the record is long, an error is indicated.
        !           123: In raw tape I/O seeks are ignored.
        !           124: A zero byte count is returned when a tape mark is read,
        !           125: but another read will fetch the first record of the
        !           126: new tape file.
        !           127: .SH FILES
        !           128: /dev/mt?,
        !           129: /dev/rmt?
        !           130: .SH "SEE ALSO"
        !           131: mt(1), tar(1), cy(4)
        !           132: .SH BUGS

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