Possible values for --compress-level and --bzip2-compress-level
peter at digitalbrains.com
Thu Feb 25 11:26:25 CET 2016
On 24/02/16 15:11, Josef Carnap wrote:
> I have a question to the options --compress-level and
> --bzip2-compress-level. Which are the supportet (possible)
> values of each of the options? -- Numbers from 0 up to 6?
The canonical way to use the BZIP2 algorithm on Linux is through the
bzip2 program. Its man page lists the following:
> -1 (or --fast) to -9 (or --best)
> Set the block size to 100 k, 200 k ... 900 k when compressing.
> Has no effect when decompressing. See MEMORY MANAGEMENT below.
> The --fast and --best aliases are primarily for GNU gzip compati‐
> bility. In particular, --fast doesn't make things significantly
> faster. And --best merely selects the default behaviour.
The other two require you to look a bit further than just lowercasing
:), but I think they both use the DEFLATE compression method. On Linux,
you will often use gzip to create archives with DEFLATE. Its man page says:
> -# --fast --best
> Regulate the speed of compression using the specified digit #,
> where -1 or --fast indicates the fastest compression method (less
> compression) and -9 or --best indicates the slowest compression
> method (best compression). The default compression level is -6
> (that is, biased towards high compression at expense of speed).
This does however raise a question:
> Here is the description of the both options in the GPG Manual:
> --bzip2-compress-level sets the compression level for the BZIP2
> compression algorithm (defaulting to 6 as well). This is a different
> option from --compress-level since BZIP2 uses a significant amount of
> memory for each additional compression level.
The defaults are apparently different?
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