https://docs.oracle.com/cd/B28359_01/server.111/b28319/ldr_field_list.htm#i1006477

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1  (hiredate  SYSDATE,
2     deptno  POSITION(1:2)  INTEGER EXTERNAL(2)
              NULLIF deptno=BLANKS,
3       job   POSITION(7:14)  CHAR  TERMINATED BY WHITESPACE
              NULLIF job=BLANKS  "UPPER(:job)",
       mgr    POSITION(28:31) INTEGER EXTERNAL 
              TERMINATED BY WHITESPACE, NULLIF mgr=BLANKS,
       ename  POSITION(34:41) CHAR 
              TERMINATED BY WHITESPACE  "UPPER(:ename)",
       empno  POSITION(45) INTEGER EXTERNAL 
              TERMINATED BY WHITESPACE,
       sal    POSITION(51) CHAR  TERMINATED BY WHITESPACE
              "TO_NUMBER(:sal,'$99,999.99')",
4      comm   INTEGER EXTERNAL  ENCLOSED BY '(' AND '%'
              ":comm * 100"
    )