99 lines
2.7 KiB
Groff
99 lines
2.7 KiB
Groff
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.TH MTIO 4
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.SH NAME
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mtio \- magnetic tape commands
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.SH SYNOPSIS
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.B "#include <sys/types.h>"
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.br
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.B "#include <sys/mtio.h>"
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.br
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.B "#include <sys/ioctl.h>"
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.SH DESCRIPTION
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.de SP
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.if t .sp 0.4
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.if n .sp
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..
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The magnetic tape devices described in
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.BR sd (4)
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may be sent commands or queried for their status using the following ioctl
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calls:
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.PP
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.RS
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.BR ioctl ( \fIfd ,
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.BR MTIOCTOP ,
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.RB & "struct mtop" )
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.br
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.BR ioctl ( \fIfd ,
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.BR MTIOCGET ,
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.RB & "struct mtget" )
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.RE
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.PP
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The struct mtop, struct mtget and associated definitions are defined in
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<sys/mtio.h> as follows:
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.PP
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.nf
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/* Tape operations: ioctl(fd, MTIOCTOP, &struct mtop) */
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.ta +4n +7n +15n
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struct mtop {
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short mt_op; /* Operation (MTWEOF, etc.) */
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int mt_count; /* Repeat count. */
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};
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.ta +17n +5n
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#define MTWEOF 0 /* Write End-Of-File Marker */
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#define MTFSF 1 /* Forward Space File mark */
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#define MTBSF 2 /* Backward Space File mark */
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#define MTFSR 3 /* Forward Space Record */
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#define MTBSR 4 /* Backward Space Record */
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#define MTREW 5 /* Rewind tape */
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#define MTOFFL 6 /* Rewind and take Offline */
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#define MTNOP 7 /* No-Operation, set status only */
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#define MTRETEN 8 /* Retension (completely wind and rewind) */
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#define MTERASE 9 /* Erase the tape and rewind */
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#define MTEOM 10 /* Position at End-Of-Media */
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#define MTMODE 11 /* Select tape density */
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#define MTBLKZ 12 /* Select tape block size */
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/* Tape status: ioctl(fd, MTIOCGET, &struct mtget) */
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.ta +4n +7n +15n
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struct mtget {
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short mt_type; /* Type of tape device. */
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/* Device dependent "registers". */
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short mt_dsreg; /* Drive status register. */
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short mt_erreg; /* Error register. */
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/* Misc info. */
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off_t mt_resid; /* Residual count. */
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off_t mt_fileno; /* Current File Number. */
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off_t mt_blkno; /* Current Block Number within file. */
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off_t mt_blksize; /* Current block size. */
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};
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.fi
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.PP
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See
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.BR mt (1)
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for a detailed description on what each operation does. The mt_type field
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is always zero, there is no use for it yet. Mt_dsreg is 0 (OK), 1 (Error),
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or 2 (EOF encountered.) Mt_erreg holds the SCSI sense key of the last
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operation. Mt_blksize is the current tape block size in bytes, zero if the
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block size is variable.
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.PP
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Note that one can issue these commands on a file descriptor that is in use
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to read or write data, something that
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.B mt
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can't do. So you can add eof markers in the middle of an output stream,
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or get the status of a device before a rewind-on-close tape rewinds.
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.PP
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The driver will automatically add an end of file marker to a tape that is
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written to if you execute a space command. If you write eof markers
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yourself then the driver will not add one extra on close.
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.SH "SEE ALSO"
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.BR mt (1),
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.BR sd (4).
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.SH AUTHOR
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Kees J. Bot (kjb@cs.vu.nl)
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