compress problem

[Michael Murphy_2]

anyone ever have a problem where you try to compress a file, but the command comes back with no error and the file is not compressed?
thanks...

[Helen French]

Which command did you use? Which OS?

[hpuxrox]

you might want to check the command itself.
what /bin/gzip or whatever.

[Ken Penland_1]

well, no, not with compress, but I have seen it with gzip, that was because I was using wildcards... are you just trying to compress a single file and typing it all out, not using wildcards?

[A. Clay Stephenson · Accepted solution]

That is entirely possible if the file is not compressible. You can use the -f option to force it. Man compress for details.

As a trivial example, do this:
cd /var/tmp
cp /dev/null xx
ls -l xx*

Now,
compress xx
You will note that no error was generated and if you now do an ls -l xx*, you will see that the file remains unchanged.

[Michael Murphy_2]

unix compress command, HP-UX 11.0. I was trying to compress the contents of a oracle cd that was copied to disk. I assume that the previos expanation about compress not making the file any smaller is the culprit.

Thanks all...

[doug mielke]

it could be that it's already compressed. (and it's possible to compress a compressed file, and have the output be even larger than the orig.)

[Bill Hassell]

Quite normal. compress does nothing if there will be no reduction in size after compressing. Binary executables are often uncompressable. If you force compression usinf -f, the resultant file(s) will generally be slightly larger than the original.

[Michael Murphy_2]

Thanks for all responses - yes the file could not be further compressed. It would just be nice if the command told you what it knows (sort of like mkdir - if you run try to make a directory that is already there - it tells you about it - go figure!!!)

[A. Clay Stephenson]

I have gone and figured and the difference is that the one case (duplicate directory is an error) and the other (an umcompressible file) is not. The system in no way corrupts or alters the file if it can't be compressed. A good analogy would be ls | grep "Furpsplat" (and I assume that you have no file named "Furpsplat") nothing is returned but it's not an error either BUT grep does let you know that nothing was matched by returning a non-zero exit status which can be determined using ${?}. In a similar manner, eventhough it is not an error, compress lets you know that nothing was done by returning 2 rather than 0 for its exit status.

This is rather typical of UNIX commands.

[Bill Hassell]

As an Southern gentleman once told me about computers:

"Y'all want friendly, yer gonna have to git yurself a dawg!"

Of course, all issues like this are easily fixed with wrappers and aliases. Just rename compress to compress.real and write a script that puts out useful messages for all the conditions.