[Rd] Possible bug: file.exists() always returns TRUE for prn.us.txt

[Joris Meys]

Thank you. I was just replying my own message with the same information.
Sorry for not doing the research properly before filing.

Cheers
Joris

On Sat, Mar 24, 2018 at 11:36 AM, Duncan Murdoch <murdoch.duncan at gmail.com>
wrote:

> On 24/03/2018 6:16 AM, Joris Meys wrote:
>
>> Dear all,
>>
>> while preparing some exercises I came across some highly surprising
>> behaviour of file.exists(). The specific value "prn.us.txt" always returns
>> TRUE, even though that file is nowhere to be found on my system.
>>
>
> That's a Windows "bug", not an R bug.  Any name starting "prn" (upper or
> lowercase), followed by an extension (i.e. a dot and characters) is taken
> to be the DOS printer device.  According to Writing R Extensions, names
> starting with "‘con’, ‘prn’, ‘aux’, ‘clock$’, ‘nul’, ‘com1’ to ‘com9’, and
> ‘lpt1’ to ‘lpt9' (possibly followed by extensions) are also bad.  You can
> Google "PRN filename in Windows" to find lots of people confused by this.
> One page I get is
>
> https://msdn.microsoft.com/en-us/library/aa365247(VS.85).aspx
>
> but there's no guarantee that will work five minutes from now.
>
> Duncan Murdoch
>
>
>
>> In a fresh R session 3.4.4 installed on Windows 10:
>>
>> grep("prn.us.txt", dir(recursive = TRUE))
>>>
>> integer(0)
>>
>>> file.exists("prn.us.txt")
>>>
>> [1] TRUE
>>
>>> file.exists("pnr.us.txt")
>>>
>> [1] FALSE
>>
>>> file.exists("prn\\.us\\.txt")
>>>
>> [1] FALSE
>>
>> sessionInfo()
>>>
>> R version 3.4.4 (2018-03-15)
>> Platform: x86_64-w64-mingw32/x64 (64-bit)
>> Running under: Windows 10 x64 (build 16299)
>>
>> Matrix products: default
>>
>> locale:
>> [1] LC_COLLATE=English_United Kingdom.1252
>> [2] LC_CTYPE=English_United Kingdom.1252
>> [3] LC_MONETARY=English_United Kingdom.1252
>> [4] LC_NUMERIC=C
>> [5] LC_TIME=English_United Kingdom.1252
>>
>> attached base packages:
>> [1] stats     graphics  grDevices utils     datasets  methods   base
>>
>> loaded via a namespace (and not attached):
>> [1] compiler_3.4.4
>>
>> This also happens in 3.4.3, 3.4.2 and 3.4.1 . It is confirmed by Roman
>> Lustrik on his system as well :
>> https://twitter.com/romunov/status/977486929380995072
>>
>> I suspect this is a bug, or I must be missing something completely.
>>
>> Cheers
>> Joris
>>
>>
>


-- 
Joris Meys
Statistical consultant

Department of Data Analysis and Mathematical Modelling
Ghent University
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