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

  $ IF F$MODE() .NES. "INTERACTIVE" THEN GOTO NON_INT_DEF
  $ INTDEF:         ! Commands for interactive terminal sessions
     .
     .
     .
  $ EXIT
  $ NON_INT_DEF:         !Commands for noninteractive processes
     .
     .
     .

      This example shows the beginning of a login.com file that has
      two sets of initialization commands: one for interactive mode
      and one for noninteractive mode (including batch and network
      jobs). The IF command compares the character string returned
      by F$MODE with the character string INTERACTIVE; if they are
      not equal, control branches to the label NON_INT_DEF. If the
      character strings are equal, the statements following the
      label INTDEF are executed and the procedure exits before the
      statements at NON_INT_DEF.