R Under development (unstable) (2025-12-16 r89184 ucrt) -- "Unsuffered Consequences"
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> message("*** devIsOpen() ...")
*** devIsOpen() ...
> 
> library("R.devices")
R.devices v2.17.3 successfully loaded. See ?R.devices for help.
> 
> for (which in list(c(), 1L, 1:5)) {
+   print(which)
+   res <- devIsOpen(which)
+   print(res)
+   stopifnot(is.logical(res))
+   stopifnot(is.character(names(res)))
+   stopifnot(length(res) == length(which))
+ }
NULL
named logical(0)
[1] 1
Device 1 
    TRUE 
[1] 1 2 3 4 5
Device 1     <NA>     <NA>     <NA>     <NA> 
    TRUE    FALSE    FALSE    FALSE    FALSE 
> 
> message("*** devIsOpen() ... DONE")
*** devIsOpen() ... DONE
> 
> proc.time()
   user  system elapsed 
   0.37    0.12    0.43