How to do str_extract with base R?

Question

I am balancing several versions of R and want to change my R libraries loaded depending on which R and which operating system I\'m using. As such, I want to stick with base

Answer 1

You could do

txt <- c("foo release 123", "bar release", "foo release 123 bar release 123")
pattern <- "release ([0-9]+)"
stringr::str_extract(txt, pattern)
# [1] "release 123" NA            "release 123"
sapply(regmatches(txt, regexec(pattern, txt)), "[", 1)
# [1] "release 123" NA            "release 123"