[R] Potential bug in readLines when reading empty lines

[Rui Barradas]

Às 15:43 de 25/06/2025, Enrico Schumann escreveu:
> 
> Quoting "Heuvel, E.G. van den (Guido) via R-help" <r-help using r-project.org>:
> 
>> Hi all,
>>
>> I encountered some weird behaviour with readLines() recently, and I am 
>> wondering if this might be a bug, or, if it is not, how to resolve it. 
>> The issue is as follows:
>>
>> If I have a text file where a line ends with just a carriage return 
>> (\r, CR) while the next line is empty and ends in a carriage return / 
>> linefeed (\r\n, CR LF), then the empty line is skipped when reading 
>> the file with readLines. The following code contains a test case:
>>
>> ---
>> print(R.version)
>> # platform       x86_64-w64-mingw32
>> # arch           x86_64
>> # os             mingw32
>> # crt            ucrt
>> # system         x86_64, mingw32
>> # status
>> # major          4
>> # minor          4.0
>> # year           2024
>> # month          04
>> # day            24
>> # svn rev        86474
>> # language       R
>> # version.string R version 4.4.0 (2024-04-24 ucrt)
>> # nickname       Puppy Cup
>>
>> txt_original <- paste0("Line 1\r", "\r\n", "Line 3\r\n")
>>
>> # Write txt_original as binary to avoid unwanted conversion of end of 
>> line markers
>> writeBin(charToRaw(txt_original), "test.txt")
>>
>> txt_actual <- readLines("test.txt")
>> print(txt_actual)
>> # [1] "Line 1" "Line 3"
>>  ---
>>
>> I included the output of this script on my machine in the comments. I 
>> would expect txt_actual to be equal to c("Line 1", "", "Line 3"), but 
>> the empty line is skipped.
>>
>> Is this a bug? And if not, how should I read test.txt in such a way 
>> that the empty 2nd line is left intact?
>>
>> Best regards,
>>
>> Guido van den Heuvel
>> Statistics Netherlands
> 
> What would be your "rule" for identifying lines? From your desired output,
> it seems \r should be end-of-line, and \n is to be ignored. Then you could
> do something like that:
> 
>    raw <- readChar("test.txt", 1000)
>    raw <- gsub("\n", "", raw)
>    strsplit(raw, "\r")[[1]]
>    ## [1] "Line 1" ""       "Line 3"
> 
> But it requires you to specify the number of characters to read (or write a
> loop).
> 
> 

Hello,

Related, output is a mess:



readChar("test.txt", n = file.size("test.txt")) |>
   textConnection() |>
   readLines()
#> [1] "Line 1" ""       ""       "Line 3" ""


Is this specific to Windows and to the way it treats "\r"? When I open 
the file in Notepad I only see two text lines, but when I open it with 
vim, it's


Line 1^M
Line 3


the carriage return is there.
(And when I paste it here


Line 1

Line 3

the <Ctrl+M> becomes an empty line.)


Hope this helps,

Rui Barradas


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