> I am using Ubuntu 11 and i have two versions of ruby 1.8.7 & 1.9.1
> and i want to uninstall ruby 1.9.1 version.I need Your help thank you!

Ubuntu is your prison.

Do not try to break out of the prison.

I did and switched to a GoboLinux approach. Every program will
have a versioned standalone directory.

My rubies would reside under:

/Programs/Ruby/1.8.7
/Programs/Ruby/1.9.1

etc..

Symlinks govern which one would be active at any one point,
the others are "hidden". This is what RVM does under the hood
as well, except it only manages ruby versions, whereas the
gobolinux approach manages all programs.

The reason that Ubuntu can not use this is because in the
/usr prefix, no same binary file can exist (nor same
library file, but they solve this by having versioned .so
files, i.e. foobar-1.0.so.1.3)

Anyway, the point is this:

This is a question you must ask Ubuntu. Ubuntu forces you
to either use their way, or the highway. I took the highway
and stopped using the archaic crippled way of distributions.

As far as I know, ubuntu uses /etc/alternatives, so perhaps
there is a way for you to make use of that. But other than
that, you should accept that you have a crippled system,
and it is the job of Ubuntu to tell you how to work around
its limitations.

RVM was suggested as alternative, which is ok - it will use
your HOME directory, with versioned directories, so this
is fine.

If you want to go the hard way and really remove 1.9.1
then do this:

in /usr/bin, remove ruby*1.9*, also irb*1.9* etc..

in /usr/lib, look for ruby site lib. For some reason it
could also be in /usr/local/lib - which is a violation of
the FHS btw. Ubuntu does not care about any standards
at all. Anyway, look at the site directory, find the
1.9* directory and remove it - only 1.8 will remain.

Then your ruby should work.

This is how I install ruby on a new system btw.

I first compile into /Programs/Ruby/VERSION_HERE,
then symlink into the /System/ hierarchy (which
is a substitute for /usr/bin /usr/lib etc..,
with subdirectories on its own), then I get
rid of the host ruby. Then I use my script to
compile a linux from scratch, and slowly eliminate
all of the host binaries (my scripts do not work
100% reliably yet, I must still manage parts of
this process on my own... but one day it will
be reliable and fully automatable)

-- 
Posted via http://www.ruby-forum.com/.