list.files changed in 2.7.0

My original message referred to the double slash and using grep. 
The particular behavior on C: wasn't the issue. For example,
list.files("C:/test1", full.names=TRUE)
[1] "C:/test1/file1" "C:/test1/file2"
list.files("C:/test1/", full.names=TRUE)
[1] "C:/test1//file1" "C:/test1//file2"
# Note the double slashes
file.exists(list.files("C:/test1", full.names=TRUE))
[1] TRUE TRUE
file.exists(list.files("C:/test1/", full.names=TRUE))
[1] TRUE TRUE
# Well that's reassuring, but I was using grep
grep("C:/test1/file2", list.files("C:/test1", full.names=TRUE))
[1] 2
grep("C:/test1/file2", list.files("C:/test1/", full.names=TRUE))
integer(0)
# bummer
In older versions of R, the last command also gave the response '2'.

While R and the OS can handle the single or double slash, grep cannot
know what I'm after.
Such unannounced changes make it harder to keep production code running
as we upgrade R versions.

It's just a fussy change, but I wondered why it was made, and whether
the behavior would change in future.

-- David

-----Original Message-----
From: henrik.bengtsson at gmail.com [mailto:henrik.bengtsson at gmail.com] On
Behalf Of Henrik Bengtsson
Sent: Tuesday, February 03, 2009 2:42 PM
To: David Reiner <davidr at rhotrading.com>
Cc: r-help at r-project.org
Subject: Re: [R] list.files changed in 2.7.0

Hi,

I've verified in "R version 2.8.1 Patched (2008-12-22 r47296)" using
both Rterm and Rgui, and

list.files(path="C:")

list the files that are in the current working directory of C: and
this *can* be changed by setwd(), that is, it does not just depend on
which directory you started R in.  The command

list.files(path="C:/")

always lists the files under the root of C:.

/Henrik
Hmm. I get exactly the same files and directories with "C:" and "C:/",
except for the double slashes now.
Previously the two calls to list.files gave exactly the same results.
My current directory (getwd()) is not C:. I'm puzzled by your output.

-- David

-----Original Message-----
From: henrik.bengtsson at gmail.com [mailto:henrik.bengtsson at gmail.com]
On
Behalf Of Henrik Bengtsson
Sent: Friday, January 23, 2009 8:36 PM
To: David Reiner <davidr at rhotrading.com>
Cc: r-help at r-project.org
Subject: Re: [R] list.files changed in 2.7.0

And I'm not sure that list.files("C:", full.names=TRUE) returns
correct pathnames, because it lists the files in the current directory
(of C:), not the root of C:. There is a difference between C: and C:/,
and you should get:

list.files("C:", full.names=TRUE)
[1] "C:aFile.txt"
[2] "C:anotherFile.txt"

list.files("C:/", full.names=TRUE)
[1] "C:/Documents and Settings"
[2] "C:/Program Files"

Now we get:

list.files("C:", full.names=TRUE)
[1] "C:/aFile.txt"
[2] "C:/anotherFile.txt"

list.files("C:/", full.names=TRUE)
[1] "C://Documents and Settings"
[2] "C://Program Files"

This causes

pathnames <- list.files("C:", full.names=TRUE);
file.exists(pathnames);

to return all FALSE (not expected), whereas,

pathnames <- list.files("C:");
file.exists(pathnames);

returns all TRUE (expected).

So, that extract slash seems to be the cause.

My $.02

/Henrik

On Fri, Jan 23, 2009 at 2:42 PM,  <davidr at rhotrading.com> wrote:
I just noticed a change in the behavior of list.files from 2.6.1pat
to
2.7.0
(I noticed it in 2.8.1 and traced back.)

Previously, if the directory ended with a slash, and full.names=TRUE,
the names
returned had a single slash at the end of the directory,
but now there are two. I noticed since I was getting a list of
certain
files and
then grepping in the list for a full name formed with a single slash.
(The double slash would be OK if I were opening the file since the OS
treats double
slash in a path the same as a single slash.)

I searched through the release notes, etc., and couldn't find this
announced.

Try
list.files("C:", full.names=TRUE)
list.files("C:/", full.names=TRUE)
Is there any chance that this could be put back to the single slash
behavior?

(This was on Windows XP.)

Thanks,
David L. Reiner

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list.files changed in 2.7.0

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