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Files Reference
cpio File Format
Purpose
Describes the copy in/out (cpio) archive file.
Description
The cpio utility backs up and recovers files. The
files are saved on the backup medium in the cpio format.
When the cpio command is used with the -c flag, the header for the cpio structure reads
as follows:
sscanf(Chdr,"%6ho%6ho%6ho%6ho%6ho%6ho%6ho%6ho%11lo%6ho%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, and other items
describing the file, are recorded in an element of the array of structures
with varying lengths.
Note
Files saved with the -c flag must be restored with the -c flag.
When the -c flag of the cpio
command is not used, the header structure contains the following fields:
h_magic |
Contains the constant octal 070707 (or 0x71c7). |
h_dev |
Device that contains a directory entry for this file. |
h_ino |
I-node number that identifies the input file to the file system. |
h_mode |
Mode of the input file, as defined in the mode.h file. |
h_uid |
User ID of the owner of the input file. |
h_gid |
Group ID of the owner of the input file. |
For remote files, these fields contain the ID after reverse translation:
h_nlink |
Number of links that are connected to the input file. |
h_rdev |
ID of the remote device from which the input file is taken. |
h_mtime |
Time when data was last modified. For remote files, this field contains
the time at the server. This time can be changed by the creat, fclearf, truncate, mknod, openx, pipe, utime, or writex subroutine. |
h_namesize |
Length of the path name, including the terminating null byte. |
h_filesize |
Length of the file in bytes. This is the length of the data section
that follows the header structure. |
h_name |
Null-terminated path name. The length of the path name, including
the null byte, is indicated by the n variable, where n equals ((h_namesize % 2) + h_namesize). That is, the n variable is equal to the h_namesize field if the h_namesize field is even. If the h_namesize field is
odd, the n variable is equal to the h_namesize field + 1. |
The last record of the archive always contains the name TRAILER!!!. Special files, directories, and the trailer are recorded
with the h_filesize field equal to 0.
Related Information
The mode.h file, stat.h file.
The cpio command, find command.
The fclear subroutine, truncate or ftruncate subroutine, mknod
subroutine, open, openx, or creat subroutine, pipe subroutine, scanf, fscanf, sscanf, wsscanf subroutine, utime subroutine, write, writex, writev, or writevx subroutine.
The Header Files Overview in AIX 5L Version 5.2 Files Reference defines
header files, describes how they are used, and lists several of the header
files for which information is provided in this documentation.
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