z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

pax header block
v An optional header block with extended header records. This header block is of
the form described in pax Header Block , with a typeflag value of x or g. The
extended header records, described in pax Extended Header , shall be included
as the data for this header block.
v A header block that describes the file. Any fields in the preceding optional
extended header shall override the associated fields in this header block for this
file.
v Zero or more blocks that contain the contents of the file.
At the end of the archive file there shall be two 512-byte blocks filled with binary
zeros, interpreted as an end-of-archive indicator.
A schematic of an example archive with global extended header records and two
actual files is shown in pax Format Archive Example. In the example, the second
file in the archive has no extended header preceding it, presumably because it has
no need for extended attributes.
Table 40. Example of a format archive for pax
USTAR Header [typeflag=g] Global Extended Header
Global Extended Header Data
USTAR Header [typeflag=x] File 1: Extended Header is included
Extended Header Data
USTAR Header [typeflag=0]
Data for File 1
USTAR Header [typeflag=0] File 2: No Extended Header is included
Data for File 2
Block of binary zeroes End of Archive Indicator
Block of binary zeroes
Description
The pax header block shall be identical to the USTAR header block described in
USTAR Interchange Format , except that two additional typeflag values are defined:
x Represents extended header records for the following file in the archive
(which shall have its own USTAR header block). The format of these
extended header records shall be as described in pax Extended Header.
g Represents global extended header records for the following files in the
archive. The format of these extended header records shall be as described
in pax Extended Header. Each value shall affect all subsequent files that do
not override that value in their own extended header record and until
another global extended header record is reached that provides another
value for the same field. The typeflag g global headers should not be used
with interchange media that could suffer partial data loss in transporting the
archive.
For both of these types, the size field shall be the size of the extended header
records in octets. The other fields in the header block are not meaningful to this
version of the pax utility. However, if this archive is read by a pax utility conforming
to the ISOPOSIX-2:1993 standard, the header block fields are used to create a
pax
Appendix H. File Formats 917