CGI script programing assistance needed

Question

I have a script, in the cgi-bin which generates this page. The intent of which is to serve as an interface for a panning web camera I built. The camera, does the pan, then quickly returns to the center position. I figured out that this is because every time the page loads, all the scripts are called, in succession, ending with z.py. How can I fix this program so that the scripts do not run until a selection occurs? As it is, everything runs when the page loads, which is why It always pans back to center.

#! /bin/sh
echo "content-type: text/html"
echo
echo "<!DOCTYPE html><html><head><title>pan camera</title></head>"
echo "<body>"

echo "<form action=\"g.pt1\" method=\"get\">"
echo "<select name=\"letter\" onchange=\"submit();\">"
echo "  <option value=\"w\">w</option>"
echo "  <option value=\"a\">a</option>"
echo "  <option value=\"s\">s</option>"
echo "  <option value=\"d\">d</option>"
echo "  <option value=\"z\">z</option>"
i=0
for i in a s d w z
        do
                echo  " $i  $(./$i.py)"
        done
echo "</select></form>"
echo "<iframe src=\"localhost:8888/?action=stream\" width=\"330\" height=\"260\">"
echo " <p>Your browser does not support iframes.</p>"
echo "</iframe>"
echo "</body></html>"

I don't think "everything runs" as you say. The for/do/echo statement lists a bunch of characters and suggests a Python file, but that's just echoed and not run. All I see here, is that upon changing the select box, `g.pt1` is invoked via CGI. Presumably that thing should pick up whether a w,a,s,d or z got selected and move the camera. If the camera moves back then I think it's due to whatever `g.pt1` is doing. — Karel Kubat, Dec 01 '14 at 12:28
$() is command substitution, so you can exec via echo. I also have some BS permission for www-data group to be allowed to access /dev/ttyACM0 — Brooke Fogg-Wolfe, Dec 07 '14 at 00:48

score 0 · Answer 1 · answered Dec 02 '14 at 01:58

Note - not a 'web programmer'...

Is the script above 'everything'? (or just the output?)

Also, for this type of use you might want to consider using a 'here document' to avoid 'escaping' all the quotes.

The FOR LOOP with the echo line in the 'middle' is run 'each time' the page loads.

$(./$i.py) will run, in order, a.py, then s.py, ... and then z.py

Remove the loop and Change this logic to 'get user input' and you should be good to go.

CGI script programing assistance needed

1 Answers1