r - remove text after final period in string

Question

I have a grep puzzle that's eluding me: I'd like to remove the text following the final period in a collection of strings (i am using R, so perl syntax is available).

For example, say the string is ABCD.txt this grep would return ABCD, and if the text was abc.com.foo.bar, it would return abc.com.foo.

Any help greatfully appreciated (i don't think i can drink any more coffee!).

Answer 1

Here are a few solutions:

sub("^(.*)[.].*", "\1", "abc.com.foo.bar") # 1
## [1] "abc.com.foo"

library(tools)
file_path_sans_ext("abc.com.foo.bar") # 3
## [1] "abc.com.foo"

ADDED. Regarding your comment asking to remove leading periods, simplest is to just feed this into any of the above where x is the input string:

sub("^[.]*", "", x)

To do any of them in one line:

x <- c("abc.com.foo.bar", ".abc.com.foo.bar", ".vimrc")

sub("^[.]*(.*)[.]?.*$", "\1", x) # 1a
## [1] "abc.com.foo.bar" "abc.com.foo.bar" "vimrc"          

file_path_sans_ext(sub("^[.]*", "", x))
## [1] "abc.com.foo" "abc.com.foo" "vimrc"