/usr/share/eccodes/definitions/mars/grib.elda.4v.def is in libeccodes-data 2.6.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | alias mars.anoffset=offsetToEndOf4DvarWindow;
alias mars.number=perturbationNumber;
|