hddtemp is a small utility (daemonizable) that gives you the temperature of your hard drive by reading S.M.A.R.T. information (for drives that support this feature).
Sync and install with pacman:
# pacman -S hddtemp
Hddtemp can be invoked with the drive as the argument:
# hddtemp /dev/sd[x]
Where x is the drive.
Running the daemon gives you the possibility to access the temperature via an TCP/IP request, so you could use this in order to check the temperature from outside, or within some scripts.
Setup with systemd
Once hddtemp has been installed, standard systemctl procedures work to start the daemon:
# systemctl start hddtemp
To start it on boot, enable it:
#systemctl enable hddtemp
Setup with legacy initscripts
Start the daemon:
# rc.d start hddtemp
Add the daemon to the DAEMONS array in /etc/rc.conf to facilitate auto-start on boot:
# DAEMONS=(... hddtemp ...)
Another way to get the temperature is by connecting to the daemon which is listening on port 7634.
$ telnet localhost 7634
Or with netcat:
$ nc localhost 7634
Refer to the manpage for information like supported drives, logging, etc.
$ man hddtemp
Hddtemp can be easily integrated with system monitors like Conky, the for GNOME Panel or the for Xfce Panel.