NAME
cpio - format of cpio archive

DESCRIPTION
The header structure, when the -c option of cpio(1) is not used,
is:

struct {
short h_magic,
h_dev;
ushort h_ino,
h_mode,
h_uid,
h_gid;
short h_nlink,
h_rdev,
h_mtime[2],
h_namesize,
h_filesize[2];
char h_name[h_namesize rounded to word];
} Hdr;

When the -c option is used, the header information is described by:

sscanf(Chdr,"%6o%6o%6o%6o%6o%6o%6o%6o%11lo%6o%11lo%s",
&Hdr.h_magic, &Hdr.h_dev, &Hdr.h_ino, &Hdr.h_mode,
&Hdr.h_uid, &Hdr.h_gid, &Hdr.h_nlink, &Hdr.h_rdev,
&Longtime, &Hdr.h_namesize,&Longfile,Hdr.h_name);

Longtime and Longfile are equivalent to Hdr.h_mtime and
Hdr.h_filesize, respectively. The contents of each file are
recorded in an element of the array of varying length structures,
archive, together with other items describing the file. Every
instance of h_magic contains the constant 070707 (octal). The
itimes h_dev through h_mtime have meanings explained in stat(2).
The length of the null-terminated path name H_name, including the
null byte, is given by h_namesize.

The last record of the archive always contains the name TRAILER!!!.
Special files, directories, and the trailer are recorded with
H_filesize equal to zero.