Windows: Backslash (\) as path separator causes error.

[fereshtehRS]

Might be by design. But on Windows it is more intuitive to use "" as path separator.

[shrektan]

I think use \\ would be ok.

[yihui]

@fereshtehRS What exactly was the error message?

@shrektan It may be okay on Windows as long as you make the assumption that your app will never run on *nix. In general I'd suggest you avoid \ since it is not portable. Is there a reason that you cannot use the forward slash / that works on both Windows and *nix?

[fereshtehRS]

For this path: read.csv("C:\Users\fereshteh\Downloads\rock.csv")

Error is:

> runApp()

Listening on http://127.0.0.1:5760
Warning in file(file, "rt") :
ock.csv': Invalid argumentrs\fereshteh\Downloads
Error in file(file, "rt") : cannot open the connection

For this path: read.csv("C:\Users\fereshteh\Downloads\rock.csv")
Error is:

> runApp()

Listening on http://127.0.0.1:5760
Error : '\U' used without hex digits in character string starting ""C:\U"

@yihui I agree that it is a good practice to use "/" instead of "". But we should at least detect and give a proper error and hint.

[wch]

@fereshtehRS, don't you need read.csv("C:\\Users\\fereshteh\\Downloads\\rock.csv")? The single backslash followed by U will make it think you're specifying a unicode value, I think.

[yihui]

Exactly. This is a general R issue: when you need a literal backslash \, use two \\.

[fereshtehRS]

Right @wch. That is the case for second error.
@yihui Also correct; error is coming from R. I wonder if Shiny could provide a better error.

[yihui]

That is also the case for the first error. It happens that \r is a legitimate control character (carriage return), and that is why the error message looks mangled (\r means move to the beginning of the current line then print the following characters).

I think this is an FAQ of R itself. Windows may be constantly surprised by the fact that they need double backslashes in file paths. I'm not sure if we really need to address this issue in Shiny.

[fereshtehRS]

Yeah, the garbled message is caused by the escaping. Unfortunately R error messages are not intuitive at all. I saw this user was totally lost when he got this error for his shiny app. Not sure what we can do about it; if nothing, then we can close this ticket.

[shrektan]

@yihui Ha, didn't notice that \\ is not portable. Luckily, I use / all the time, so never meet problems on Linux env... Thanks any way.

[yihui]

@fereshtehRS I completely agree this is fairly confusing to those who do not understand the escaping rules in R. It may be possible to detect such problems with a certain linter (https://github.com/rstudio/rsconnect/blob/master/R/linters.R), but I'm not the right person to decide if this is worth it (given it is not an issue specific to shiny) or work on it.

[fereshtehRS]

@yihui I'll close this; agree that it is not a priority.