I'm running Arch Linux. Today i have tried to update my system, there was an error when trying to update "glibc" package. I don't remember correctly what was the error message (something about "/usr/lib/modules" moved to "/lib/modules"). Now, i know that "glibc" is VERY important for the system, but i just wanted to try something crazy - install new "glibc" after i delete the old one with "sudo pacman -Rnn glibc". It turned out to be VERY bad idea, after removing old "glibc" my system can't recognize "sudo", "dir" and other commands so i can't install new "glibc". Can you suggest me some solution? How to get out of this situation? :)
glibc (or some other C library) is required for virtually everything in a Linux system. Removing it is a Really Bad Idea, as you've discovered the hard way.
The easiest way to recover from this is to boot from the Arch Linux CD and reinstall glibc to your system. One possible way to do this is provided on the Arch Wiki.