On 21/07/2009 5:03 PM, Jim Nemesh wrote:
Hi! I'm wondering if there's a smart way around this:
fileName= (some valid file on your system)
> fileCon=file(fileName, open="rt")
> l<-readLines (fileCon, n= 1)
>
> isOpen(fileCon)
[1] TRUE
> close(fileCon)
> isOpen(fileCon)
Error in isOpen(fileCon) : invalid connection
How do you test for a file being closed if isOpen gives you an error
message?
You could use try().
But you shouldn't be doing that. Whoever opens the connection should
close it. The isOpen() test is designed to be used on newly created
connections, being passed to some other function and guaranteed to be
valid. Was it created with file(fileName, open="rt") or file(fileName)?
That's what isOpen() is there to determine. (The first one was
opened, and should be closed by whoever opened it; the second one was
not, and the function that uses it shouldn't leave it open.)
Duncan Murdoch
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