TP(5) File Formats Manual TP(5)NAME
tp - DEC/mag tape formats
DESCRIPTION
Tp dumps files to and extracts files from DECtape and magtape. The formats of these tapes are the same except that magtapes have larger
directories.
Block zero contains a copy of a stand-alone bootstrap program. See reboot(8).
Blocks 1 through 24 for DECtape (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:
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;
};
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 (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 direc-
tory entry is zero.
Blocks above 25 (resp. 63) are available for file storage.
A fake entry has a size of zero.
SEE ALSO fs(5), tp(1)BUGS
The pathname, uid, gid, and size fields are too small.
7th Edition May 15, 1985 TP(5)
Check Out this Related Man Page
TAR(5) File Formats Manual TAR(5)NAME
tar - tape archive file format
DESCRIPTION
Tar, (the tape archive command) dumps several files into one, in a medium suitable for transportation.
A ``tar tape'' or file is a series of blocks. Each block is of size TBLOCK. A file on the tape is represented by a header block which
describes the file, followed by zero or more blocks which give the contents of the file. At the end of the tape are two blocks filled with
binary zeros, as an end-of-file indicator.
The blocks are grouped for physical I/O operations. Each group of n blocks (where n is set by the b keyletter on the tar(1) command line
-- default is 20 blocks) is written with a single system call; on nine-track tapes, the result of this write is a single tape record. The
last group is always written at the full size, so blocks after the two zero blocks contain random data. On reading, the specified or
default group size is used for the first read, but if that read returns less than a full tape block, the reduced block size is used for
further reads.
The header block looks like:
#define TBLOCK 512
#define NAMSIZ 100
union hblock {
char dummy[TBLOCK];
struct header {
char name[NAMSIZ];
char mode[8];
char uid[8];
char gid[8];
char size[12];
char mtime[12];
char chksum[8];
char linkflag;
char linkname[NAMSIZ];
} dbuf;
};
Name is a null-terminated string. The other fields are zero-filled octal numbers in ASCII. Each field (of width w) contains w-2 digits, a
space, and a null, except size and mtime, which do not contain the trailing null and chksum which has a null followed by a space. Name is
the name of the file, as specified on the tar command line. Files dumped because they were in a directory which was named in the command
line have the directory name as prefix and /filename as suffix. Mode is the file mode, with the top bit masked off. Uid and gid are the
user and group numbers which own the file. Size is the size of the file in bytes. Links and symbolic links are dumped with this field
specified as zero. Mtime is the modification time of the file at the time it was dumped. Chksum is an octal ASCII value which represents
the sum of all the bytes in the header block. When calculating the checksum, the chksum field is treated as if it were all blanks. Link-
flag is NULL if the file is ``normal'' or a special file, ASCII `1' if it is an hard link, and ASCII `2' if it is a symbolic link. The
name linked-to, if any, is in linkname, with a trailing null. Unused fields of the header are binary zeros (and are included in the check-
sum).
The first time a given i-node number is dumped, it is dumped as a regular file. The second and subsequent times, it is dumped as a link
instead. Upon retrieval, if a link entry is retrieved, but not the file it was linked to, an error message is printed and the tape must be
manually re-scanned to retrieve the linked-to file.
The encoding of the header is designed to be portable across machines.
SEE ALSO tar(1)BUGS
Names or linknames longer than NAMSIZ produce error reports and cannot be dumped.
4.2 Berkeley Distribution November 7, 1985 TAR(5)