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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 direc-
       tory; 8 entries per block; 64 bytes per entry.  Each entry has the fol-
       lowing 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 directory 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.



                                15 January 1983                          TP(5)