How to Parse Config.fpw Programmatically

• Microsoft Visual FoxPro for Windows, versions 3.0 and 3.0b

SUMMARY

This article shows by example how to parse through a text file programmatically. This example uses Config.fpw. The code searches for a specific entry, and then it modifies the entry if it is found or adds it if not found.

You might want to use this technique in distributed applications, for example, to control the operating environment.

MORE INFORMATION

This code example checks to determine if the Visual FoxPro system variable MVCOUNT is less than 2000. If follows this process:

1. Open or Create the Config.fpw file as applicable,

2. Search through the Config.fpw file for the MVCOUNT= entry.

   a. If it finds an entry, it modifies it to read MVCOUNT=2000.

   b. If it doesn't find an entry, it creates one.

3. Write the modified file contents back to disk, and close the file.

Code Sample

* Parsefpw.prg * ------------ * To make this backward compatible to FoxPro 2.x, replace the MESSAGEBOX() * functions with WAIT WINDOWs *

cNewLine   = "MVCOUNT=2000"+CHR(13)      && This is the line to change/add
nUpdateStat = 0                          && Use to determine which message

nFileHand   = FOPEN(cVFPConfigLoc, 2)    && open with read/write privileges
IF nFileHand == -1                       && Can't find Config.fpw
  nFileHand = FCREATE(cVFPConfigLoc, 0)  && Create an Config.fpw
  IF nFileHand == -1                     && Can't create Config.fpw
    = FCLOSE(nFileHand)
    nUpdateStat = 1                      && Not existing, Cannot Create
  ELSE
    = FWRITE(nFileHand, cNewLine)
    = FCLOSE(nFileHand)
    nUpdateStat = 2                      && Not existing, Did Create
  ENDIF

  filesize = FSEEK(nFileHand, 0, 2)
  = FSEEK(nFileHand, 0, 0)               && position file pointer to BOF
  contents = FREAD(nFileHand, filesize)
  spos = RAT("MVCOUNT", UPPER(contents)) && from right to find last

  IF spos <> 0                           && Contains "MVCOUNT" entry
    * len = length (for example, len=20+1=21 for "MVCOUNT = 30 ")
    * len = AT(CHR(13)+CHR(10), SUBSTR(contents, spos)) - 1 && w/o CR & LF
    len = AT(CHR(13)+CHR(10), SUBSTR(contents, spos)) + 1 && with CR & LF
    IF LEN = 0
      LEN = LEN(SUBSTR(contents, spos))
    ENDIF
  ELSE                                   && "MVCOUNT" Not there, append it
    LEN = AT(CHR(26), contents)          && CHR(26) = Escape = EOF marker
    IF LEN <> 0
      contents = LEFT(contents, LEN - 1)
      LEN = 0
    ENDIF
    spos = RAT(CHR(13)+CHR(10), contents, ;
    IIF(RIGHT(contents, 2) <> CHR(13)+CHR(10), 1, 2))
    spos = spos + IIF(spos = 0, 1, 2)
  ENDIF
  contents = STUFF(contents, spos, LEN, cNewLine)
  = FSEEK(nFileHand, 0, 0)
  = FWRITE(nFileHand, contents)
  = FCHSIZE(nFileHand, LEN(contents))
  = FCLOSE(nFileHand)
  nUpdateStat = 3                           && Did exist, Modified

       +"startup directory. This file must contain an

       +"statement in order for the <YourApp> application to

       +"correctly."+CHR(13)+CHR(13)

  =MESSAGEBOX(cMsg1+;
    +"The computer system could not find this file nor could it"+CHR(13);
    +"create one. Until one exists, <YourApp> cannot be used.",0)

  =MESSAGEBOX(cMsg1+;
    +"The <YourApp> startup directory did not include this"+CHR(13);
    +"file so one was created for you. The new Config.fpw file"+CHR(13);
    +"contains all the required settings for the <YourApp>"+CHR(13);
    +"application to run."+CHR(13)+CHR(13);
    +"In order to activate this statement you need to RESTART the"+CHR(13);
    +"<YourApp> application.",0)

  =MESSAGEBOX(cMsg1+;
    +"Your existing Config.fpw file has now been modified to

    +"an MVCOUNT=2000 statement. To activate this statement you

    +"to RESTART the <YourApp> application.",0)