ZIP File Format
1. Zip
properties
ID: 44562f82-60b6-4d89-9346-c0d5525e86c8
CREATED:
see also: PKWare (PKZIP, Phil Katz)
In a Unix environment tarballs are usually preferred, although zip files can be optimal in specific scenarios due to the difference in design - Zip files interweave compression and archival.
- zip files contain one or more files or directories
A ZIP file is correctly identified by the presence of an end of central directory record which is located at the end of the archive structure in order to allow the easy appending of new files. If the end of central directory record indicates a non-empty archive, the name of each file or directory within the archive should be specified in a central directory entry, along with other metadata about the entry, and an offset into the ZIP file, pointing to the actual entry data. This allows a file listing of the archive to be performed relatively quickly, as the entire archive does not have to be read to see the list of files. The entries within the ZIP file also include this information, for redundancy, in a local file header. Because ZIP files may be appended to, only files specified in the central directory at the end of the file are valid. Scanning a ZIP file for local file headers is invalid (except in the case of corrupted archives), as the central directory may declare that some files have been deleted and other files have been updated.
The ZIP format uses specific 4-byte "signatures" to denote the various structures in the file. Each file entry is marked by a specific signature. The end of central directory record is indicated with its specific signature, and each entry in the central directory starts with the 4-byte central file header signature.
The minimum size of a .ZIP file is 22 bytes. Such an empty zip file contains only an End of Central Directory Record (EOCD): 50 4B 05 06 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
The maximum size for both the archive file and the individual files inside it is 4,294,967,295 bytes (232 − 1 bytes, or 4 GiB minus 1 byte) for standard ZIP. For ZIP64, the maximum size is 18,446,744,073,709,551,615 bytes (264 − 1 bytes, or 16 EiB minus 1 byte)