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

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Appendix H. File Formats
This information gives more detailed information on the formats of the files used by
the shell commands. The file formats are:
v cpio
v magic
v pax
v queuedefs
v tags
v tar
v utmpx
v uucp
cpio — Format of cpio archives
Description
You can use the cpio command to back up or restore files. The cpio command
reads and writes either a compact binary format header or an ASCII format header.
The tar command reads and writes headers in either the original TAR format from
UNIX systems or the USTAR format defined by the POSIX 1003.1 standard.
The pax command reads and writes headers in any of the cpio formats.
A cpio archive consists of one or more concatenated member files. Each member
file contains a header optionally followed by file contents as indicated in the header.
The end of the archive is indicated by another header describing an (empty) file
named TRAILER!!.
There are two types of cpio archives, differing only in the style of the header:
v ASCII archives have totally printable header information; thus, if the files being
archived are also ASCII files, the whole archive is ASCII.
v By default, cpio writes archives with binary headers. However, binary archive
files cannot usually be ported to other operating systems, so you should not use
these.
The information in an ASCII archive header is stored in fixed-width, octal (base 8)
numbers padded with zeros on the left. Table 39 gives the order and field width for
the information in the ASCII header:
Table 39. Archive File: ASCII Header
Field Width Field Name Meaning
6 magic Magic number 070707
6 dev Device where file resides
6 ino I-number of file
6 mode File mode
6 uid Owner user ID
6 gid Owner group ID
6 nlink Number of links to file
6 rdev Device major/minor for special file
11 mtime Modify time of file
6 namesize Length of filename
11 filesize Length of file
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