[R] handling a cancelled file.choose()

[Ben Tupper]

Hello,


I have a file reading function that prompts the user with a file dialog 
if a filename is not provided in the argument list.  It is desirable to 
return gracefully if the user selects "Cancel", but file.choose() throws 
an error instead of returning something like a character.

 > file.choose()
[1] "/Users/ben/ben_idl.pref"

 > file.choose()
Error in file.choose() : file choice cancelled

I naively planned to use nchar() to test the length, assuming 
cancellation would return a zero-length character. That appears to be 
out of the question. Are there other options available in the base package?

Thanks!
Ben