TP(5) File Formats Manual TP(5)NAME
tp - DEC/mag tape formats
DESCRIPTION
The command 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 bproc(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];
int mode;
char uid;
char gid;
char unused1;
char size[3];
long modtime;
int tapeaddr;
char unused2[16];
int 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 filsys(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.
Blocks above 25 (resp. 63) are available for file storage.
A fake entry has a size of zero.
SEE ALSO filsys(5), tp(1)BUGS
The pathname, uid, gid, and size fields are too small.
TP(5)
Check Out this Related Man Page
tar(5) File Formats Manual tar(5)Name
tar, mdtar - tape archive file format
Description
The tape archive command dumps several files, including special files, into one, in a medium suitable for transportation.
A 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 option on the command line, and the
default is 20 blocks) is written with a single system call; on 9-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 following is an example of a header block:
#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];
char rdev[6]
} dbuf;
};
The name field is a null-terminated string. The other fields are 0-filled octal numbers in ASCII. Each field (of width w) contains w
minus 2 digits, a space, and a null, except size and mtime , which do not contain the trailing null. The name field specifies the name of
the file, as specified on the command line. Files dumped because they were in a directory that was named in the command line have the
directory name as prefix and /filename as suffix. The field specifies the file mode, with the top bit masked off. The uid and gid fields
specify the user and group numbers that own the file. The size field specifies the size of the file in bytes. Links and symbolic links
are dumped with this field specified as zero. The mtime field specifies the modification time of the file at the time it was dumped. The
chksum field is a decimal 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. The linkflag field is ASCII 0 if the file is normal or a special file and ASCII 1 if it
is a hard link, and ASCII 2 if it is a symbolic link. The name to which it is linked, if any, is in linkname, with a trailing null.
Unused fields of the header are binary zeros and are included in the checksum. The rdev field encodes the ASCII representation of a device
special file's major and minor device numbers.
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 rescanned to retrieve the linked file.
The encoding of the header is designed to be portable across machines.
Restrictions
Names or link names longer than NAMSIZ produce error reports and cannot be dumped.
See Alsotar(1)tar(5)