.help zzclmt May84 "System Interface"
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NAME
zzclmt -- close a magtape file
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SYNOPSIS
.nf
zzclmt (chan, mode, nrecords, nfiles, status)

int	chan			# OS channel of magtape file
int	mode			# access mode of file
int	nrecords		# number of records skipped
int	nfiles			# number of filemarks skipped
int	status
.fi
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DESCRIPTION
The magtape file associated with the channel \fIchan\fR is closed, i.e., the
magtape device is freed for use by another process and the channel is freed
for use with another file.  Closing a magtape file does not free the magtape
device for use by another user; the drive must also be \fBdeallocated\fR
before it can be accessed by another user.  If \fImode\fR is WRITE_ONLY an
end of tape (EOT) mark is written at the current position of the tape.
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RETURN VALUE
ERR is returned in \fIstatus\fR if \fIchan\fR is invalid or if the tapemark
could not be written.
The number of file records skipped when the tape was closed in returned
in \fInfiles\fR.
The number of filemarks skipped when the tape was closed in returned
in \fInfiles\fR.
A negative value is returned if the tape was backspaced.
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NOTES
If error recovery occurs while positioning the tape, i.e., during a call
to \fBzzopmt\fR, \fBzzclmt\fR will be called with \fImode\fR set to READ_ONLY.
Otherwise the mode given is that given when the tape was opened.

If a magtape file is opened for writing and immediately closed without writing
anything a zero length file may be written, i.e., an EOT mark.  If another
file is then appended the new file will be unreachable once the tape is
rewound.  To avoid this problem the high level code writes a short record
containing the ASCII string "NULLFILE" before closing the tape.
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SEE ALSO
zzopmt, zfiomt, system.deallocate
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