Regex match after last / and first underscore

Question

Assuming I have the following string:

string = "path/stack/over_flow/Pedro_account"

I am intrested in matching the first 2 characters after the last / and before the first _. So in this case the desired out put is:

Pe

What I have so far is a mix of substr and str_extract:

substr(str_extract(string, "[^/]*$"),1,2)

which of course will give an answer but I belive there is a nice regex for it as well, and that is what I'm looking for.

Answer 1

Using basename to get the last folder name, then substring:

substr(basename("path/stack/over_flow/Pedro_account"), 1, 2)
# [1] "Pe"

Answer 2

Remove everything till last / and extract first 2 characters.

Base R -

string = "path/stack/over_flow/Pedro_account"
substr(sub('.*/', '', string), 1, 2)
#[1] "Pe"

stringr

substr(stringr::str_remove(string, '.*/'), 1, 2)

Answer 3

You can use str_match with a capture group:

• / Match literally
• ([^/_]{2}) Capture 2 chars other than / or _ in group 1
• [^/]* Match optional chars other than /
• $ End of string

See a regex demo and a R demo.

Example

library(stringr)
string = "path/stack/over_flow/Pedro_account"
str_match(string, "/([^/_]{2})[^/]*$")[,2]

Output

[1] "Pe"