Osmium

What is Osmium

a fast and flexible C++ toolkit and framework for working with OSM data (libosmium)
a command line tool that uses the Osmium C++ library (osmium-tool)
a Python wrapper for the C++ library (PyOsmium)
a NodeJS wrapper for the C++ library (node-osmium) (not maintained any more)

Get information about an OSM file
Convert OSM files from one format into another. This includes all XML and PBF formats as well as the OPL format, the o5m format and an easy to read "debug" format.
Merge and apply OsmChange files to an OSM file (with or without history)
Extract a geographical area from an OSM data or history file
Extract data by keys or tags
Extract data from OSM history files (Planet.osm/full) for a given point in time or a time range
And many more things...

There are also many more tools based on libosmium, you can find some of them at https://osmcode.org/ or https://github.com/osmcode/.