The Get Value of CLI Symbol routine requests the calling
    process's command language interpreter (CLI) to return the value
    of a CLI symbol as a string. LIB$GET_SYMBOL then returns the
    string to the caller. Optionally, LIB$GET_SYMBOL can return the
    length of the returned value and the table in which the symbol
    was found.

    Format

      LIB$GET_SYMBOL  symbol ,resultant-string [,resultant-length]

                      [,table-type-indicator]