gsub and regex to tidy comma-limited values

I am cleaning up comma-limited values, so that only one comma
separates each value. Using the example below, as much as I try with
regex, I can't remove the last comma. I hope to have a one-liner
solution, if possible.

gsub("^,*|,*$|(,)*", "\\1", ",,,apple,,orange,,,,,lemon,strawberry,,,,")
[1] "apple,orange,lemon,strawberry,"

I am cleaning up comma-limited values, so that only one comma
separates each value. Using the example below, as much as I try with
regex, I can't remove the last comma. I hope to have a one-liner
solution, if possible.

gsub("^,*|,*$|(,)*", "\\1", ",,,apple,,orange,,,,,lemon,strawberry,,,,")
[1] "apple,orange,lemon,strawberry,"

sub(",$","",gsub("^,*|,*$|(,)*", "\\1",
",,,apple,,orange,,,,,lemon,strawberry,,,,"))

It may not be the best solution, but it was my first thought

Tom

----- Original Message ----- From: "Daren Tan" <darentan76 at gmail.com>
To: <r-help at r-project.org>
Sent: Saturday, March 14, 2009 6:42 PM
Subject: [R] gsub and regex to tidy comma-limited values

I am cleaning up comma-limited values, so that only one comma
separates each value. Using the example below, as much as I try with
regex, I can't remove the last comma. I hope to have a one-liner
solution, if possible.

gsub("^,*|,*$|(,)*", "\\1", ",,,apple,,orange,,,,,lemon,strawberry,,,,")
[1] "apple,orange,lemon,strawberry,"