Hi,
I'd like to know the command to unpack a file in the form pdf.pdf or ps.ps.When I run it through an archiver,it says it's either a gzip or a bunzip file.But how do I do it from the console?Please help.

pdf files are portable document files that are best opened with Adobe Acrobat Reader, though there are other apps in Linux. ps files are postscript files which you could open with GIMP or several other apps. GIMP will also open pdf files.

They shouldn't have the file extension listed twice, at any rate. Perhaps the person who prepared the file made a mistake?

At any rate, they're not zipped files.

Well,I tried just renaming the file,but it didn't help.I opened it using an archiving utility and it said that the file was in bzp2 format.It unpacked it alright.It certainly doesn't seem to be a mistake on the author's part,coz I come across many files with such extensions.And I ask the guys who prepare and they say it is a compressed file.So it is,coz after the decompress it shows an increase in file size.
And of course i know how to open pdf and ps files.I use pdf's every day at home and at the university.What really foxes me is as to how does the archiver guess what compress type the file has?please advise.

From a short identifier at the beginning of the file. You can see the file type with the file command, eg 'file my_file.pdf'. file gets its data from the magic file, in my system it's in /usr/share/file. Type 'man file' and 'man magic' for a more comprehensive explanation.

LasseW,

Not to hijack the thread, but thanks for the info. How
does this work with an encrypted file? Example:

mingdao@james:~$ file Oct_newsletter.pdf.gpg
Oct_newsletter.pdf.gpg: data

Same thing ...

It's an encrypted file, and without the password
it obviously won't be able to tell WHAT you have
in it ... might be mp3, xls or pdf....

If I send you a something in a gift-wrapped box
looking at the box won't tell you anything about
the content (not in detail, of course) ... it may say
on the customs form that it's a present, and that
it's e.g. a Linux-CD. But to get what it REALLY is
you need to open the box.



Cheers,
Tink