https://cpp.openfoam.org/v9/timeActivatedFileUpdate_8H_source.html
fileUpdate1
{
type timeActivatedFileUpdate;
libs ("libutilityFunctionObjects.so");
writeControl timeStep;
writeInterval 1;
fileToUpdate "$FOAM_CASE/system/fvSolution";
timeVsFile
(
(-1 "$FOAM_CASE/system/fvSolution.0")
(0.10 "$FOAM_CASE/system/fvSolution.10")
(0.20 "$FOAM_CASE/system/fvSolution.20")
(0.35 "$FOAM_CASE/system/fvSolution.35")
);
}