如何检测文件使用的压缩类型? (如果没有指定文件扩展名)

如何检测文件所使用的压缩类型？(假设。拉链。GZ.未指定 xz 或任何其他扩展名)。

这些信息是否存储在文件头的某个地方？

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As an alternative to inspecting the file header by hand, you could use some utility like TrID. The link points to the cross-platform command line version; for Windows there's a GUI, too.

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If you're on a Linux box just use the 'file' command.

http://en.wikipedia.org/wiki/File_(command)

$ mv foo.zip dink
$ file dink
dink: gzip compressed data, from Unix, last modified: Sat Aug  6 08:08:57 2011,
max compression
$
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最佳答案

You can determine that it is likely to be one of those formats by looking at the first few bytes. You should then test to see if it really is one of those, using an integrity check from the associated utility for that format, or by actually proceeding to decompress.

You can find the header formats in the descriptions:

Others:

  • zlib (.zz) format description, starts with two bytes (in bits) 0aaa1000 bbbccccc, where ccccc is chosen so that the first byte viewed as a int16 times 256 plus the second byte viewed as a int16 is a multiple of 31. e.g: 01111000(bits) = 120(int16), 10011100(bits) = 156(int16), 120 * 256 + 156 = 30876 which is a multiple of 31
  • compress (.Z) starts with 0x1f, 0x9d
  • bzip2 (.bz2) starts with 0x42, 0x5a, 0x68
  • Zstandard (.zstd) format description, frame starts with a 4 byte magic number using little-endian format 0xFD2FB528, a skipable frame starts with 0x184D2A5? (question mark is any value from 0 to F), and dictionary starts with 0xEC30A437.
  • A few more formats in the magic database from the file command
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If you want to determine an algorithm used to compress a linux kernel, there is a script for that, see this question and answer: https://unix.stackexchange.com/a/553192/264065


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