I'm new to Linux (Debian) world. Irssi requires GLib, so I installed 2.6.6 version. When trying ./configure Irssi, it gives:
...
checking pkg-config is at least version 0.7... yes
checking for GLIB - version >= 2.6.0...
*** 'pkg-config --modversion glib-2.0' returned 2.6.6, but GLIB (2.32.4)
*** was found! If pkg-config was correct, then it is best
*** to remove the old version of GLib. You may also be able to fix the error
*** by modifying your LD_LIBRARY_PATH enviroment variable, or by editing
*** /etc/ld.so.conf. Make sure you have run ldconfig if that is
*** required on your system.
*** If pkg-config was wrong, set the environment variable PKG_CONFIG_PATH
*** to point to the correct configuration files
no
*** trying without -lgmodule
checking for pkg-config... (cached) /usr/local/bin/pkg-config
checking pkg-config is at least version 0.7... yes
checking for GLIB - version >= 2.6.0...
*** 'pkg-config --modversion glib-2.0' returned 2.6.6, but GLIB (2.32.4)
*** was found! If pkg-config was correct, then it is best
*** to remove the old version of GLib. You may also be able to fix the error
*** by modifying your LD_LIBRARY_PATH enviroment variable, or by editing
*** /etc/ld.so.conf. Make sure you have run ldconfig if that is
*** required on your system.
*** If pkg-config was wrong, set the environment variable PKG_CONFIG_PATH
*** to point to the correct configuration files
no
*** If you don't have GLIB, you can get it from ftp://ftp.gtk.org/pub/glib/
*** We recommend you get the latest stable GLIB 2 version.
*** Compile and install it, and make sure pkg-config finds it,
*** by adding the path where the .pc file is located to PKG_CONFIG_PATH
configure: error: GLIB is required to build irssi.
Can someone enlighten what's the deal?
Packages for libraries are split into at least two packages--one for the shared library itself, which is what you need in order to run software which uses the library, and another for the extra stuff necessary to compile software which depends on that library. In Debian, the names for those packages are libglib-2.0 and libglib-2.0-dev.
You had version 2.32.2 of libglib-2.0 installed, but in order to compile software like irssi you need libglib-2.0-dev. The right thing to do would be to install that package:
sudo apt-get install libglib-2.0-dev
Unfortunately, installing an ancient version of glib like you did (2.6.6 was released on 2005-08-01) may have broken your system pretty badly, since it is likely other software depends on a much newer version of glib. If you didn't pass any arguments to ./configure it probably installed into /usr/local, which would be good because it may not have overwritten anything you needed in /usr (which is where the packaged version gets installed). So, you may be able to just go into the directory you compiled 2.6.6 in and run:
sudo make uninstall
You'll probably also want reinstall the package from Debian, too:
sudo apt-get install --reinstall libglib-2.0
I don't know what you're trying to do with irssi, but instead of installing it from the tarball, you may want to just use the Debian package:
sudo apt-get install irssi
Unless you're actually modifying the code, you almost never want to install from tarballs (or git, for that matter). I suggest you find whatever graphical package manager you have installed--what that package is depends on the version of Debian as well as which desktop environment you chose, but likely choices are GNOME Software Center or Synaptic.