sudo gem install iStats
istats
--- CPU Stats ---
CPU temp: 61.13°C ▁▂▃▅▆▇
--- Fan Stats ---
Total fans in system: 1
Fan 0 speed: 4867 RPM ▁▂▃▅▆▇
--- Battery Stats ---
No battery on system
For more stats run `istats extra` and follow the instructions.