Path of Installed package for pkg-config

Some times when we are installing some package in linux , the installer is unable to find some installed package on your system. If you are sure that you the package is already installed on your system, but the installer keeps on telling that it is unable to detect package, you may need to set the environment variable PKG_CONFIG_PATH to tell the installer where to find package installation. For example, if you are install Xfce4 and the installer is keep telling the GTK+ is not found and you know that it is installed than you need to specify the path of gtk+ topkg-config , here you find that you installed Gtk+ into /opt/gtk2, you may need to execute the command

PKG_CONFIG_PATH="/opt/gtk2/lib/pkgconfig:$PKG_CONFIG_PATH"
export PKG_CONFIG_PATH

Of if you don't know the path than search for pkgconfig file for that package.