IBM AS/400E manual Writing Common Gateway Interface Programs

information that was written to stdout. This will cause the web browser to display a ″Document Contains No Data″ error message. Another application could run again in the same activation group that properly erased stdout. In this instance, the data that has been buffered from previous calls would be sent.

#include <stdio.h> void main(void) {

/***************************************************/

/* Write header information.*/ /***************************************************/ printf("Content-type: text/html\n\n");

/***************************************************/

/* Write header information.*/ /***************************************************/ printf("Hello World\n");

}

End processing may not erase stdio buffers so the application must erase the stdout with a fflush(stdout) call. The following example will work regardless of the activation group specification:

#include <stdio.h> void main(void) {

/***************************************************/

/* Write header information.*/ /***************************************************/ printf("Content-type: text/html\n\n");

/***************************************************/

/* Write header information.*/ /***************************************************/ printf("Hello World\n");

/*-------------------------------------------------	*/
/* FIX: Flush stdout.	*/
/*-------------------------------------------------	*/
fflush(stdout);

}

When run in a *NEW activation group, this example CGI would read CONTENT_LENGTH bytes of data from stdin and write this back out to stdout. The system has allocated the buffer that is used to hold the data with a malloc. Like the example that is previously shown, this application is relying on several aspects of job end processing to function properly.

If this CGI program were built to run in either a user-named or *CALLER activation group, the following problems would occur:

vAs with the simple example that is previously shown, the application is not erasing stdout. This would cause the web browser to display a ″Document Contains No Data″ error message. You could run another application again in the same activation group that properly erased stdout. This would send the data that has been buffered from previous calls.

vStdin is buffered similar to stdout. If the contents of stdin are not erased, the stdin data on the second and all following calls of the CGI program will be unpredictable and the contents may at times contain information from subsequent requests.

Chapter 1. Writing Common Gateway Interface Programs 19