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HP-UX 11i Version 3: February 2007

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cpio — format of cpio archive


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

struct { short c_magic, c_dev; ushort c_ino, c_mode, c_uid, c_gid; short c_nlink, c_rdev, c_mtime[2], c_namesize, c_filesize[2]; char c_name[c_namesize rounded to word]; } Hdr;

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

sscanf(Chdr,"%6ho%6ho%6ho%6ho%6ho%6ho%6ho%6ho%11lo%6ho%11lo", &Hdr.c_magic,&Hdr.c_dev,&Hdr.c_ino,&Hdr.c_mode, &Hdr.c_uid,&Hdr.c_gid,&Hdr.c_nlink,&Hdr.c_rdev, &Longtime,&Hdr.c_namesize,&Longfile);

Longtime and Longfile are equivalent to Hdr.c_mtime and Hdr.c_filesize, respectively. The contents of each file are recorded together with other items describing the file. Every instance of c_magic contains the constant 070707 (octal). The items c_dev through c_mtime have meanings explained in stat(2). The length of the null-terminated path name c_name, including the null byte, is given by c_namesize.

The last record of the archive always contains the name TRAILER!!!. Directories and the trailer are recorded with c_filesize equal to zero.

It will not always be the case that c_dev and c_ino correspond to the results of stat(), but the values are always sufficient to tell whether two files in the archive are linked to each other.

When a device special file is archived by HP-UX cpio (using the -x option), c_rdev contains a magic constant which is dependent upon the implementation doing the writing. H_rdev flags the device file as an HP-UX 32-bit device specifier, and c_filesize contains the 32-bit device specifier (see stat(2)). If the -x option is not present, special files are not archived or restored. Non-HPUX device special files are never restored.


cpio: XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1

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