/usr/share/eccodes/definitions/mars/grib.mnth.fg.def is in libeccodes-data 2.0.2-5.
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 7 8 9 10 | #if(centre == ECMWF ) {
#meta fgDate validity_date(dataDate,dataTime,endStep) : no_copy;
#meta fgTime validity_time(dataDate,dataTime,endStep) : no_copy;
#alias mars.date = fgDate;
#alias mars.time = fgTime;
#alias mars.step = startStep;
#}
label "x";
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