/usr/share/geometry_msgs/msg/Quaternion.msg is in libgeometry-msgs-dev 1.12.3-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | # This represents an orientation in free space in quaternion form.
float64 x
float64 y
float64 z
float64 w
|