compress (Unix)
From Just Solve the File Format Problem
- This article is about a specific file format. For compression in general, see Compression.
compress is a Unix command line utility, and a general-purpose compressed file format. Its compression algorithm is based on LZW.
Contents |
Identifiers
The conventional filename extension is a capitalized .Z.
Identification
Files begin with bytes 1f 9d.
See also
- SCO compress LZH - variant
- Quasijarus Strong Compression - variant
- pack (Unix) - predecessor
- compact (Unix) - predecessor
- Squash (RISC OS)
- compact (Gene Olson)
Formats that could be considered to be the successors of compress include Freeze/Melt, and (especially) Gzip.
The 0x1f compression family
There are several compressed file formats, with similar features, that begin with byte value 0x1f (octal 037; decimal 31). We arbitrarily choose compress as the representative example, and list the formats here.
| Signature (hex) | Format |
|---|---|
1f 1e |
pack (Unix) |
1f 1f |
pack (Unix) - old format |
1f 8b |
gzip |
1f 9d |
compress |
1f 9e |
Freeze/Melt - old format |
1f 9f |
Freeze/Melt - new format |
1f a0 |
SCO compress LZH |
1f a1 |
Quasijarus Strong Compression |
1f ff or ff 1f |
compact (Unix) |
