/sys$common/syshlp/helplib.hlb Lexicals, F$DEVICE, Example  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  $ START:
  $     DEVICE_NAME = F$DEVICE("*0:","DISK","RA60")
  $     IF DEVICE_NAME .EQS. "" THEN EXIT
  $     SHOW SYMBOL DEVICE_NAME
  $     GOTO START

      This command procedure displays the device names of all the
      RA60s on a unit numbered 0.

      Because no stream-id argument is specified, F$DEVICE uses an
      implicit search stream. Each subsequent use of the F$DEVICE
      function uses the same search criteria to return the next
      device name. After the last device name is displayed, the
      F$DEVICE function returns a null string and the procedure
      exits.