Open System Services System Calls Reference Manual (G06.29+, H06.08+, J06.03+)

Files cpio(4)
The archive entry for the name of a file has the following format:
Table 11−2. cpio Archive File Filename Entry Format
Field Name Length (in octets) Interpretation
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c_name c_namesize Pathname string
The c_name field contains the pathname of the file as a string with the length given by the
c_namesize field in the file header. This string length includes the null character that terminates
the name. If the filename is found on a medium that would create an invalid pathname, the pax
utility skips the file and displays an error message to the standard error file.
Following the header and the pathname string, the cpio archive file data has the following form:
Table 11−3. cpio Archive File Data Format
Field Name Length (in octets) Interpretation
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c_filedata c_filesize Data
If the c_filesize field of the header has the value 0 (zero), then the file is empty.
A header denoting the filename TRAILER!!! indicates the end of the archive; what follows this
header is undefined.
Only regular files contain data that can be restored. FIFO special files, directories, and the trailer
are archived with the c_filesize field of the header equal to 0 (zero); these objects are restored
with the pax utility as directories and FIFOs.
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