Unshorten URLs in Tableau with R

tc17_03_url_unshorten.txt

SCRIPT_STR('
  newurl <- .arg1
  url <- ""
  while(url != newurl){
    data <- system(toString(paste0("curl -I ", newurl)), intern=T)
    if(sum(grepl("location: ", tolower(data))) == 0){
      url <- newurl
    }else{
      data <- subset(data, tolower(substring(data, 1, 9))=="location:")
      stringurl <- substring(data[1], 11, nchar(data[1])-1)
      if(substring(stringurl, 1, 4)=="http"){ 
        newurl <- stringurl
      }else{
        url <- newurl
      }
    }
  }
  return(newurl)
',
ATTR([URL Extract]))