[Rd] Guidelines when to use LF vs CRLF ("\n" vs. "\r\n") on Windows for new lines (line endings)?

[Duncan Murdoch]

On 25/07/2020 4:48 p.m., nospam using altfeld-im.de wrote:
> Dear R developers,
> 
> I am developing an R package which returns strings with new line codes.
> I am not sure if I should use "\r\n" or "\n" in my returned strings on Windows platforms.
> 
> What is the recommended best practice for package developers (and code in base R) for coding new lines in strings?
> 
> And just out of curiosity: What is the reason (or history) for preferring "\n" in R even on Windows (see examples below)?

Most Windows run-times (including the version of MSVCRT that R uses) 
convert \n to \r\n on text files, so you rarely need an explicit \r\n. 
That's the difference between type text and type binary on connections.

Duncan Murdoch


> 
> Best regards
> 
> Jürgen
> 
> PS: Examples from base R:
> 
> R seems to use (almost) only "\n" for new lines internally - even on Windows platforms, eg.:
> 
>      charToRaw(paste0("a", "\n", "b"))
>      [1] 61 0a 62
> 
>      # eol default is "\n"
>      write.table(x, file = "", append = FALSE, quote = TRUE, sep = " ",
>                  eol = "\n", na = "NA", dec = ".", row.names = TRUE,
>                  col.names = TRUE, qmethod = c("escape", "double"),
>                  fileEncoding = "")
> 
> On the other hand some external interfaces require Windows-style new lines ("\r\n"), eg. text file outputs seen ti care internally:
> 
>      writeLines(text, con = stdout(), sep = "\n", useBytes = FALSE)
>      # Excerpt from the documentation:
>      #     Normally writeLines is used with a text-mode connection,
>      #     and the default separator is converted to the normal separator
>      #     for that platform (LF on Unix/Linux, CRLF on Windows).
> 
>      # calls internally do_writelines():
>      # https://github.com/wch/r-source/blob/8db7b85953127f364f52d201ec057911db4601e5/src/main/connections.c#L4023
>      # But: Where is the conversion done (hidden in the call to Riconv()?)
> 
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