sudo pacman -Syyu
sudo pacman -S [something to install]
should I restart just to be safe?
If there are updates to the kernel, glibc or systemd, you may want to restart so the updated versions are in use. If you have, say, updates to your desktop environment, a simple logout/login is enough.
The best way is to find what programs/services use the old libraries and restart them. And you can achieve it by listing all used files using 'lsof' and find those that have 'DEL' type. DEL means filename was removed from the filesystem but it is still stuck in memory because someone uses it.
Here is the full command line:
The only mandatory reason to reboot is a new kernel (and you can soft-reboot using kexec). See https://wiki.archlinux.org/index.php/Kexec for details, in short:
Little bit improved version that gives systemd service names:
Note that there are some issues: