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diff --git a/sys/mtio/mtrewind.x b/sys/mtio/mtrewind.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<error.h>
+include	"mtio.h"
+
+# MTREWIND -- Rewind the named magtape device.  This is a synchronous
+# rewind.  Rewind not only rewinds the device, it also initializes the
+# MTIO view of what is on the tape (number of files, total bytes used).
+# Hence, if the drive is left allocated but the tape is changed, or if
+# the position cache becomes inaccurate for any reason, a rewind will
+# initialize things without having to deallocate and reallocate the drive.
+
+procedure mtrewind (mtname, initcache)
+
+char	mtname[ARB]		#I device to be rewound
+int	initcache		#I discard positional information?
+
+pointer	sp, fname
+int	fd, mtopen()
+errchk	mtfname
+
+begin
+	call smark (sp)
+	call salloc (fname, SZ_FNAME, TY_CHAR)
+
+	# Init position cache.
+	if (initcache == YES) {
+	    call mt_glock (mtname, Memc[fname], SZ_FNAME)
+	    iferr (call delete (Memc[fname]))
+		;
+	}
+
+	# Rewind device.
+	call mtfname (mtname, 1, Memc[fname], SZ_FNAME)
+	iferr (fd = mtopen (Memc[fname], READ_ONLY, 0))
+	    call erract (EA_WARN)
+	else
+	    call close (fd)
+
+	call sfree (sp)
+end