[Proj] Proj4 cs2cs Program and the Geocentric Coord System

[Ung]

Hi All,

I found that running the following command:
cs2cs +proj=geocent +ellps=WGS84 +to +proj=geocent +ellps=WGS84

with input "123 655 123" yields "-122.87 -654.29 -122.86"

As I understand it, the command would project a point from a geocentric
frame to the same frame, which should result in a point with the same
coordinates. Why the difference in output? I have only recently stepped into
the shallow parts of the deep waters of geodesy, having only learnt the term
"geodetic" two weeks ago...So while it may not be meaningful to call the
command above, I wonder if the output is as expected, and if so, I would
definitely appreciate someone setting my understanding right.

Thanks.
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