R shell.exec requires full file path

Question

I installed R and RStudio this week on a new Windows 10 machine. I want to use this R code to launch Excel and open a CSV file that is in a subdirectory of the current working directory:

file <- "example.csv"
sub_dir <- "subdirectory"
shell.exec(file.path(sub_dir, file))

But I get this error:

Error in shell.exec(file.path(sub_dir, file)) : 
  'subdirectory/example.csv' not found

However, if I provide shell.exec with the full file path, this code works as expected:

shell.exec(file.path(getwd(), sub_dir, file))

The documentation for shell.exec states:

The path in file is interpreted relative to the current working directory.

R versions 2.13.0 and earlier interpreted file relative to the R home directory, so a complete path was usually needed.

Why doesn't my original code (without getwd) not work? Thanks.

Answer 1

It looks to be related to the path separator in some wacky way. Below, I specify the the file path separator as \ and the command executes as expected. You could keep your call to file.path() and simply wrap in normalizePath() as another option.

file <- "example.csv"
sub_dir <- "subdirectory"
dir.create(sub_dir)
writeLines("myfile",file.path(sub_dir, file))
# Works
shell.exec(file.path(sub_dir, file, fsep = "\\"))
shell.exec(file.path(sub_dir, file))
#> Error in shell.exec(file.path(sub_dir, file)): 'subdirectory/example.csv' not found