Date: Sun, 31 Aug 2003 00:32:05 +0200 From: pbdlists@pinboard.com To: FreeBSD-Questions@freebsd.org Subject: Re: zmore for bzip2? Message-ID: <20030831003205.A94657@pinboard.com> In-Reply-To: <3F50CF19.5030200@mac.com>; from cswiger@mac.com on Sat, Aug 30, 2003 at 12:21:45PM -0400 References: <200308271100.42049.dkelly@HiWAAY.net> <20030828043747.GA1206@terminator.client.attbi.com> <20030829235939.GE42454@grumpy.dyndns.org> <3F50CF19.5030200@mac.com>
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Adapting zmore for the case where you specify the files to display on
the command line is not problem at all:
> diff kk zmore
5,14d4
< get_decompressor ()
< {
< case `file ${1--} | sed "s/[^:]*: *\([^ ]*\).*/\1/"` in
< "compress"*) DECOMPRESSOR="uncompress -c";;
< "gzip"*) DECOMPRESSOR="gzip -cdfq";;
< "bzip2"*) DECOMPRESSOR="bunzip2 -cdq";;
< *) DECOMPRESSOR="cat";;
< esac
< }
<
56,57c46
< get_decompressor ${FILE}
< ${DECOMPRESSOR} "$FILE" | eval ${PAGER-more}
---
> gzip -cdfq "$FILE" | eval ${PAGER-more}
But when zmore is used as a pipe or with input redirection, things become
more complicated.
gzip -cdfq | eval ${PAGER-more}
In order to detect the type of data passed on STDIN, the get_decompressor
function or any other means of detection would consume STDIN. STDIN, however
must be passed to the decompressor after the type of data has been
detected. I don't have an idea hot to 'duplicate' STDIN, so it could be
consumed twice. Sure, writing it to a temporary file would be a
workaround:
38,53c28
< FILE="/tmp/.zmore.${$}"
< touch ${FILE} 2>/dev/null
< if [ "${?}" -ne "0" ]; then
< echo "can't create temporary file"
< exit 1
< fi
< chmod 0600 ${FILE}
< cat >${FILE}
< if [ "${?}" -ne "0" ]; then
< echo "can't create temporary file"
< rm -f ${FILE}
< exit 1
< fi
< get_decompressor ${FILE}
< cat ${FILE} | ${DECOMPRESSOR} | eval ${PAGER-more}
< rm -f ${FILE}
---
> gzip -cdfq | eval ${PAGER-more}
But I don't like that. I myself sometimes work with compressed files
larger than anything I would be happy to write to /tmp or somewhere else
(even though those cases usually rather use zcat and its cousinds than
zmore...)
Kurt
On Sat, Aug 30, 2003 at 12:21:45PM -0400, Chuck Swiger wrote:
> David Kelly wrote:
> [ ... ]
> > Yes, of course. But zmore is smart enough to figure out what to do with
> > several compression techniques, or even to handle non-compressed files
> > very trivially and without hassle.
>
> 'zmore' is a simple shell script which calls "gzcat | ${PAGER-more}". One
> solution to your problem, or at least a solution, would be to change zmore to
> look for a trailing bz/bz2 or invoke bzcat instead. Another would be to change
> the sources of gzip to recognize the bzip2 magic files bytes, extending the
> detection of gzip versus classic LZH used by compress.
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