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Is there a way to print the decompressed size of a .bz2 file without actually decompressing the entire thing?

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So there is no metadata about the original file in the bzip output? >:( – endolith Oct 11 '09 at 22:30
not that i've seen reference to. :/ – quack quixote Oct 11 '09 at 22:35

2 Answers 2

up vote 17 down vote accepted

As noted by others, bzip2 doesn't provide much information. But this technique works -- you will have to decompress the file, but you won't have to write the decompressed data to disk, which may be a "good enough" solution for you:

$ ls -l foo.bz2
-rw-r--r-- 1 ~quack ~quack 2364418 Jul  4 11:15 foo.bz2

$ bzcat foo.bz2 | wc -c         # bzcat decompresses to stdout, wc -c counts bytes
2928640                         # number of bytes of decompressed data

You can pipe that output into something else to give you a human-readable form:

$ ls -lh foo.bz2
-rw-r--r-- 1 quack quack 2.3M Jul  4 11:15 foo.bz2

$ bzcat foo.bz2 | wc -c | perl -lne 'printf("%.2fM\n", $_/1024/1024)'
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Well, that only took five minutes of 100% CPU to calculate. – endolith Oct 11 '09 at 22:39
only? AND it would fill up a disk? i've got a compressed tarball of an old linux install that's only 407meg yet took my poor ancient server 30-45 minutes to extract. that included writing to disk, tho, i'll have to run that script to time it. get back to ya in half an hour... :) – quack quixote Oct 11 '09 at 23:12
I picked the smallest file for the first test, of course. 140 MB compressed --> 3 GB uncompressed. The larger files are 5 GB compressed... – endolith Oct 12 '09 at 4:50
heh .. lemme know how big the 5GBs turn out to be... and how long it takes to figure it out via this XD – quack quixote Oct 12 '09 at 5:25

The program bzip2 unfortunately doesn't have a list parameter.

If a programmer, I suppose you would need to use libbzip2 to write a small program for doing it.

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