tp.5

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)tp.5	8.1	9/11/90
.TH tp 5 "" "" Unsupported
.SH Name
tp \- DEC/mag tape formats
.SH Description
The
.PN tp
file
dumps files to and extracts files from
magtape.
The formats of these tapes are the same except
that magtapes have larger directories.
.PP
Block zero contains a
copy of a stand-alone bootstrap program.
For further information, see reboot(8).
.PP
Blocks 
1 through 62 for magtape
contain a directory of the tape.
There are 192 (resp. 496) entries in the directory;
8 entries per block;
64 bytes per entry.
Each entry has the following format:
.EX
struct {
	char	pathname[32];
	unsigned short	mode;
	char	uid;
	char	gid;
	char	unused1;
	char	size[3];
	long	modtime;
	unsigned short	tapeaddr;
	char	unused2[16];
	unsigned short	checksum;
};
.EE
.PP
The path name entry is the path name of the
file when put on the tape.
If the pathname starts with a zero word,
the entry is empty.
It is at most 32 bytes long and ends in a null byte.
Mode, uid, gid, size and time modified
are the same as described under i-nodes.  For further information, 
see file system fs(5).
The tape address is the tape block number of the start of
the contents of the file.
Every file
starts on a block boundary.
The file occupies (size+511)/512 blocks
of continuous tape.
The checksum entry has a value such that
the sum of the 32 words of the directory entry is zero.
.PP
Blocks above 25 (resp. 63) are available for file storage.
.PP
A fake entry
has a size of zero.
.SH See Also
tp(1), fs(5)