ipv4_regex <- "^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$" #' Convert a vector of IPv4 addresses to in-addr.arpa format #' #' @md #' @param ipv4 vector of ipv4 addresses #' @export to_inaddr_arpa <- function(ipv4) { ifelse( test = grepl(ipv4_regex, ipv4), yes = paste0( c( rev(unlist(strsplit(ipv4, ".", 4), use.names = FALSE)), "in-addr.arpa." ), sep = "", collapse = "." ), no = ipv4 ) }