Shell Programming and Scripting

in the instance of a file compressed with compress to a .Z extension...

how would I, in the Bourne Shell, capture its compression ratio? Gunzip returns -1 and I'd then gone down the track of roughly calculating the ratio (not including time) manually.

Until I found out the Bourne Shell doesn't do calculations!

So I am perplexed. I am stuck in the Bourne Shell, I'm not permitted to use anything else - what function returns the compression ratio in a manner I can capture.

There was one process with a -v verbose option but it would not pipe to echo or > to a file from memory.

Strategically stuck is the phrase.

wow I'm using the UNIX bc calculator within bourne which to me is a pretty cool way to get away with not leaving and still doing calculations lol...

but if anyone gets a better idea how to grab the 'real' compression ratio for a .Z file I'd greatly appreciate the insight.

thanks

wow - the bc calculator!

Try..

Code:

set $(gzip -v file.txt 2>&1)
echo $2

hi Igor, thanks but it gives me a syntax error

syntax error: '(' unexpected

could you recommend a good quality tutorial page on the uses of set - I don't really see much sense in the man pages for this one...

a tutorial with generalised examples would make it clearer

i understand set on itself has all of he name=value pairs for my environment but beyond that I think I need to do some reading.

thanks

could someone explain with set why this isn't possible?

Code:

set `compress -v fileX` > fileY.txt

I am clearly missing something here.
Suppose you have a compressed file with name = file.Z. The compression ratio is the number of bytes in the original divided by the number of bytes in the compressed file.

Code:

oldsize=`zcat file.Z | wc -l`
newsize=`ls -l file.Z | awk '{print $4}' `
comp_ratio=`echo $oldsize / $newsize | bc -l`