[X-Unix] How to *quietly* unarchive a .bz2 file?

[Jerry Krinock]

For remote diagnosis of problems, I have a script which unarchives .bz2 system logs, filters them for certain keywords, and zips the resulting text into an archive which the user can email to me.

This works except that for unarchiving the .bz2 logs, I use /usr/bin/open, which launches the Archive Utility app, which opens a Finder window that activates for each .bz2 file, creating visual pollution and intercepting any keystrokes which the user might be typing in another app.  Very annoying.

Archive Utility.app is in /System/Library/CoreServices and has no documentation.

It appears that on Linux, people use 'bunzip' or 'tar -x' for this.  Well, bunzip seems to not exist on Mac OS X, and although 'man tar' says that "this implementation recognizes bzip2 compression automatically when reading archives", it doesn't work on a .bz2…

JerryMacMini:~ jk$ tar -x -f /var/log/system.log.0.bz2
tar: This does not look like a tar archive
tar: Skipping to next header
tar: Archive contains obsolescent base-64 headers
tar: Error exit delayed from previous errors

I get the same problem if I use the -j option (which, according to 'man tar', is not necessary for extracting)

JerryMacMini:~ jk$ tar -x -j -f /var/log/system.log.0.bz2
tar: This does not look like a tar archive
tar: Skipping to next header
tar: Archive contains obsolescent base-64 headers
tar: Error exit delayed from previous errors

How can I quietly unarchive a .bz2 file?

Thanks,

Jerry