INFO: Appending from a Delimited ASCII File Using Low-Level I/O (115418)

SUMMARY

When you are importing data from other applications into FoxPro, a delimited ASCII file is often used. However, if any of the data columns from the original database extend beyond 255 characters, any text beyond this point will be cut off. Text longer than 255 characters should be stored in a FoxPro memo field. However, the APPEND FROM command does not move data into memo fields.

To work around this behavior, you can use the low-level file I/O functions in FoxPro to programmatically move the data from the text file into the database including the memo field. A sample program for doing this is provided below.

MORE INFORMATION

The program below is provided as an example of a FoxPro program that employs low-level file I/O to append data from a delimited text file into character and memo fields. For purposes of this article, the input text file contains three character fields. The third field is to be placed in a memo field and might contain embedded carriage returns.

A sample delimited text file might be constructed as follows:

   "FRED","FLINTSTONE","A movie about Barney and Betty"
   "RENO","RAINES","The Renegade"

The following program will add this data to the database:

   *MYMEMO.PRG
   m.numchars=0
   m.end=.F.
   m.bytestoend=0
   IF USED("mymemo")
      SELECT mymemo
   ELSE
      IF FILE("mymemo.dbf")
         USE mymemo IN 0
         SELECT mymemo
      ELSE
         CREATE TABLE mymemo (first C(10), LAST C(15), details m(10))
      ENDIF
   ENDIF
   H=FOPEN("mymemo.txt",10)
   IF ! H<0
      m.totalchars=FSEEK(H,0,2)  && how many characters in file?
      =FSEEK(H,0,0)              && go back to start

      DO WHILE (! EOF(H) ) AND (! m.end)
         m.first=""
         m.last=""
         m.details=""
         FOR m.numfields = 1 TO 3
            DO CASE
               CASE m.numfields=1
                  m.field="m.first"
               CASE m.numfields=2
                  m.field="m.last"
               CASE m.numfields=3
                  m.field="m.details"
            ENDCASE
            m.numquotes=0
            DO WHILE m.numquotes < 2 AND (! m.end)
               in_char=FREAD(H,1)
               DO CASE
                  CASE in_char=["]
                     m.numquotes=m.numquotes+1
                  CASE m.numquotes=1 AND ;
                   (ASC(in_char)=32 OR (ASC(UPPER(in_char))>64 ;
                   AND ASC(UPPER(in_char))<91))
                     STORE EVALUATE(m.field)+m.in_char TO (m.field)
               ENDCASE
               m.numchars=m.numchars+1
               IF m.numchars = m.totalchars   && are we at the end?
                  m.end=.T.                   && set our own EOF marker
               ENDIF
            ENDDO
         ENDFOR
         APPEND BLANK
         GATHER MEMVAR MEMO
      ENDDO
      =FCLOSE(H)
   ENDIF

For information about using low-level file commands to export data to a delimited ASCII file, please see the following article in the Microsoft Knowledge Base:

95722 How to Export Memo Fields to an ASCII File