Save excel or csv to local server

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1

I read an excel file with parametrized rmd.
Running Rstudio Server Open Source
Can choose the file from a local directory with

params:
        datum: "2022-11-14"
        data:
                label: "Input dataset:"
                value: results.xls
                accept: ".xls"
                input: file

After modification (prediction from a model) I want to write the file back to the same location. Any ideas?
Thanks
Peter

2 
xlsx::write.xlsx(x, file, sheetName = "Sheet1", 
  col.names = TRUE, row.names = TRUE, append = FALSE)
3

Thanks. That's not the problem.
As suggested I now save it locally, using openxlsx.
Two advantages: no Java, can modify the date format, which caused problems.
Then I use the export function within the file panel. Then I can use it within my server structure.

Peter