There are several old postings that may help:

• Watching long processes through CGI by merlyn
• Update on controlling long-running processes via CGI
• Managing a long running server side process using CGI

So the PDF file would be created at the same time the log data is created, and I'm not sure how I would get them both from separate requests.

I've just updated an old SANE CGI frontend wrapping scanimage to run on an embedded system. It does something roughly similar: In the scan handler, scanimage emits progress messages that are sent to the browser, while the scanned image is stored in a temp file on the server. The last action of the progress display is to emit a download link (for browsers with Javascript disabled) and a Javascript redirection to that link. The handler for the download link just sends the content of the temp file.

In theory, there should be some code to remove old temp files (e.g. a cron job, a cleanup routine invoked for every request, or simply a call to unlink at the end of the download handler). The CGI should also use individual temp files for each scan. But there is exactly one user for the scanner (me), the CGI frontend is only available in my local network, and I don't care about having an old scan remaining on the scan server, so I use the same temp file for all scans, and I don't even bother to lock the file.

Alexander

Unless you want to do something klunky like wrap the response as JSON (return an Object with a key for the log text and one for the PDF contents (maybe base64-encoded)) you're thinking along the wrong lines. You're going to need to keep context on the server and handle returning things in multiple HTTP requests.

The way I'd approach is to assign some kind of "job id" to a set of results (the input file, the output dvi or pdf, the log from processing). When you process an input file you'd maintain the context (the results) in some way keyed by the job id (save everything into a temporary directory named after it perhaps). You'd then come up with an API that you can use from clients to request back a result type for a given job id and either link directly or (possibly using some sort of JS) provide an all in one page (maybe fetching the log and pdf and showing those, with a separate link to the pdf results for download).