Extracts a substring from the input character string using a
       default edit string of 30 characters.

1  –  Input

       This function takes three parameters:

       o  A character string

       o  An ordinal number of starting character (numerical position
          within string)

       o  The length of desired substring

2  –  Output

       A substring.

3  –  Example

       DTR> DECLARE WOMBAT PIC X(25).
       DTR> WOMBAT = "Wombats have sharp claws."
       DTR> PRINT FN$STR_EXTRACT (WOMBAT,9,4)

                  FN$STR
                  EXTRACT

       have

       DTR>