Radegast is good. Installing it on later MacOS is a bit troublesome, you need X-Quartz (X11) and a very specific version of Mono, 2.10.9_12 to be installed first.
Get Radegast from source forge. http://radegast.sourceforge.net/wiki/Radegast_Download
For Mac, first install Mono: http://download.mono-project.com/archive/2.10.9/macos-10-x86/12/MonoFramework-MDK-2.10.9_12.macos10.xamarin.x86.dmg
and then, for Mac, XQuartz: https://www.xquartz.org
It also works on Linux, you may use the same install as Mac, but you may not need the X-Window system noted above, I'm not certain about that.
and finally install Radegast
That's not running it from a command line, but is probably the lightest weight viewer that you'll come across!