Base R

In Windows to get the computer name in it’s fully qualified form you need to do:

paste(Sys.getenv("COMPUTERNAME"),
  Sys.getenv("USERDNSDOMAIN"),
  sep=".")
## [1] "SLOCKE.MANGO.LOCAL"

In Linux, you can use:

Sys.getenv("HOSTNAME")
## [1] ""

Each of these returns an empty string in the other OS so you can concatenate them to get the FQDN.

getFQDN <- function (){
  tolower(
           paste0( paste(Sys.getenv("COMPUTERNAME"),
                        Sys.getenv("USERDNSDOMAIN"),
                        sep=".")
                 , Sys.getenv("HOSTNAME")
                 )
  )
}
getFQDN()
## [1] "slocke.mango.local"

Using iptools

Alternatively, we could use the iptools package (available from CRAN) which now also works in Windows.

library(iptools)
ip_to_hostname("127.0.0.1")
## [[1]]
## [1] "slocke.Mango.local"

For more info on iptools, check out the GitHub repo.