is there a way to achieve this with compress?

Shell Programming and Scripting
1

I'm trying to figure out how I can get an equivalent output to a text file such as if I use

gunzip -l filename

in that gunzip will output the previous file size and the compressed size and the ratio...

is there a way to achieve this with compress and zip?

i am very new at shell scripting and i seem to be getting documentation eyes but little result...

if anyone could offer a bit of quick advice I would greatly appreciate it, thanks.

2

at the moment I have this piece of code...

gzip helpme
gunzip -l helpme > file
gunzip helpme
compress helpme
gunzip -l helpme >> file
gunzip helpme
zip helpme
zip helpme.zip helpme
gunzip -l helpme.zip >> file
gunzip helpme.zip

as you can see I am simply compressing and decompressing this helpme file three times - gzip, compress and zip - and am trying to get their respective before and after and compression percentage for comparison. I'll use awk later to display it.

So my question is really how do I get over the fact that gunzip -l outputs non gzip files as uncompressed -1 and ratio 0.0%?

If anyone could steer me on course with this I would greatly appreciate it. I'm determined to get on top of this and just have the feeling I'm missing something.

3

If you are trying to compress an already compressed file you don't gain much, in fact it is possible to lose - in the sense that the compressed compressed file is larger than the compressed file.

try gzip -9 <filename>

to get maximum compression.

If you are trying archive a bunch of files, tar them first, then compress the tarball. tar will allow you to archive .gz files.

4

sorry I must not have explained properly... all I am trying to do at this point is compress using 3 ways... zip, gzip and compress... and output the results into a file for comparison... which I will use awk to output the results sorted by best compression...

... a single file only

this is just an exercise and I'm not looking for code but rather general advice on how to go about it

thanks for the response anyway :wink: