[archlinux]error while loading shared libraries: libreadline.so.5

error while loading shared libraries: libreadline.so.5: cannot open shared object file: No such file or directory
解決方法：

Boot an Arch live, mount your Arch partition in /mnt

(指令 mount /dev/sdax /mnt 注:x是分割)and run

Code:

pacman -r /mnt -Sy bash

You should always upgrade the system with pacman -Syu and never upgrade single packages.