500 error: how do you return output to CGI?

pgmarlin · - Joined: 06 Nov 2004 Posts: 2

I wrote the following simple Foxpro program to execute as a CGI script

******************************************************************************
FUNCTION TestCGI

********** store 2 carriage return/line feeds ********
gcCRLF = CHR(13) + CHR(10)

******** store output string ***********
lcOut = "HTTP/1.0 200 OK" + gcCRLF + “Content-type: text/html”;
+ gcCRLF + gcCRLF ;
+ “<html>The current time is : “ + TIME() + “</html>“

********* copy output strint to text file *************
STRTOFILE(lcOut,”c:\ScriptOut.txt')

************* return output string to CGI ???? ***************
RETURN lcOut
******************************************************************************

In case you do not speak “Fox”, the program simply

1. Creates an output string variable that includes a header and html
2. Writes the string to a file C:\ScriptOut.txt
3. Retuns the string (hopefully to CGI for serving to the client)

Steps 1 and 2 ran properly and C:\ScriptOut.txt contained the following

---------------------------------------------------------------------------
HTTP/1.0 200 OK
Content-type: text/html

<html>The current time is : 23:18:53</html>
---------------------------------------------------------------------------
However, I received Error 500 - Internal Server Error
How do I get my output string back to STDOUT? If I write it to the screen (similar to DOS’s ECHO command), I still get the 500 error.

Thank you for any help you can give.
Paul Marlin

admin · Site Admin Joined: 03 Mar 2002 Posts: 1300

Your program should write the string to STDOUT in order to be CGI compliant.
But Error 500 can also happen for other reasons. For example, if Abyss is unable to run the CGI interpreter for some reason (usually, it is caused by PATH problems and missing DLLs.)

pgmarlin · - Joined: 06 Nov 2004 Posts: 2

Thank you for the response. Using the sample Visual Basic CGI program that I downloaded from the Abyss website, I determined that I have to use the Kernel32.dll in order to

1. get a file handle for Stdout using GETSTDHANDLE(-11)

2. write the output using WRITEFILE

and I was able to successfully translate the sample into Visual Foxpro and produce a web page.

NOW, can you suggest how to read the form variables (POST Method) from stdin? I tried using

1. GETSTDHANDLE(-10) and

2. READFILE

Both GETSTDHANDLE(-10) and READFILE returned zero.

The VB sample showed using -10& as the parameter for GETSTDHANDLE, but I don’t know what “&” is, since it is not used in Visual Foxpro.

Incidently the dll declarations I used were

DECLARE long GetStdHandle IN kernel32.dll long handleInput
DECLARE long ReadFile IN kernel32.dll ;
long filehandle, string buffer,;
long BytesToRead, long @ BytesRead, long OptionalPar
DECLARE long WriteFile IN kernel32.dll ;
long filehandle, string buffer, long BytesToWrite, ;
long @ BytesWritten

the successful write command was

WRITEFile(lnOutputHandle, lcOutString, LEN(lcOutString), lnBytesWritten)

(I did not have to use the optional 5th parameter)

The unsuccessful read commands were

lcBuffer = SPACE(5000)
lnRead = 0
lnResult = READFILE(lnInputHandle, lcBuffer, 5000,lnRead,0)

The fith parameter was not optional; if I omitted it, I got an “exception” error.

Incidently, is there any chance that the web server creates a temporary file from stdin that i could read?

Any help would be appreciated.