R regex remove all punctuation except apostrophe [duplicate]

Answer 1

You could use:

str2 <- "this doesn't not have an apostrophe,.!@#$%^&*()"

library(qdap)
strip(str2, apostrophe.remove = FALSE, lower.case = FALSE)

Answer 2

I am not sure if you can specify all punctuations except ' within a regexp the way you've done. I would check for alphanumerics + ' + space with negation:

gsub("[^'[:lower:] ]", "", str2) # per Joshua's comment
# [1] "this doesn't not have an apostrophe"

Answer 3

A "negative lookahead assertion" can be used to remove from consideration any apostrophes, before they are even tested for being punctuation characters.

gsub("(?!')[[:punct:]]", "", str2, perl=TRUE)
# [1] "this doesn't not have an apostrophe"