R Under development (unstable) (2024-06-25 r86831 ucrt) -- "Unsuffered Consequences"
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> library(foreign)
> 
> DF <- data.frame(X1 = 1:3, X2 = 4:6, X3 = paste0("str_", 1:3), 
+                  stringsAsFactors = FALSE)
> 
> write.foreign(DF, "datafile.dat", "codefile.sps", "SPSS")
> 
> files <- c( "datafile.dat", "codefile.sps")
> for(f in files) tools::Rdiff(f, file.path("keep", f))
> unlink(files)
> 
> proc.time()
   user  system elapsed 
   0.26    0.07    0.32