TAR(F)                                     UNIX System V



     Name
          tar - archive format


     Description
          The command tar(C) dumps files to and  extracts  files  from
          backup media or the hard disk.

          Each file is archived in contiguous blocks, the first  block
          being occupied by a header, whose format is given below, and
          the subsequent blocks of the files occupying  the  following
          blocks.   All  headers and file data start on 512 byte block
          boundaries  and  any  spare  unused  space  is  padded  with
          garbage. The format of a header block is as follows:

          #define TBLOCK 512
          #define NBLOCK 20
          #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 extno[4];
                    char extotal[4];
                    char efsize[12];
               } dbuf;
          } dblock;

          The name entry is the path name of the file  when  archived.
          If the pathname starts with a zero word, the entry is empty.
          It is at most 100 bytes long and ends in a null byte.  Mode,
          uid,  gid, size, and time modified are the same as described
          under i-nodes (refer to filesystem(F)).  The checksum  entry
          has  a value such that the sum of the words of the directory
          entry is zero.

          If the entry corresponds to a link, then  linkname  contains
          the  pathname  of the file to which this entry is linked and
          linkflag is set to 0 if there are no links, or  1  if  there
          are links.  No data is put in the archive file.

     See Also
          filesystem(F), tar(C)


     Standards Conformance
          tar is conformant with:

          AT&T SVID Issue 2, Select Code 307-127.


     (printed 8/23/89)                                  TAR(F)