I recently found a .graphml file but have no idea how to open it from command line. Do I need to install something to view such files in ubuntu from command line? I tried google but could not find any result related to this topic.
Graphml is the standard file format for graph yED editor. This editor can be downloaded on any platform (linux, mac ,windows).
The documentation about the graphml format itself, xml-based, can be found here.