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Old 04-12-2004, 08:24 PM   #1
LQ Newbie
Registered: Sep 2003
Location: Canada
Distribution: Fedora & Gentoo-uClinux
Posts: 15

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Form processing with cgi and uclinux

Hi, I read tutorials on cgi.... cant find that much help. I have a question.

I am working with a dragonball mc68k processor running uClinux. I will be installing the BOA webserver on this board. The board will control some lights. Either lights on or lights off. Now I want to put control in a web site so I can connect to the web site anywhere and turn on my house lights via web page. I have the C program written that will control the lights.
I want to do the following very simple form.

 <INPUT TYPE="radio" NAME="state" VALUE="Y">LightsON<BR>
 <INPUT TYPE="radio" NAME="state" VALUE="N">LightsOFF<BR>
 <INPUT TYPE="submit" NAME="button" VALUE="Send">

So when some one selects lights on, it will execute a cgi script that will call a c program that turns on a light.( the web server will be hosted on a NETdimm processor, the processor is connected to a light and the c program controls the light(on/off).

I want to implement this in a web site, so when a user goes to the web site they use the form on the website and select on or off in the form for lights.

So Do I write a shell script that calls the C program? or a shell script that calls a cgi script which inturn calls my C lights program
eval "`cgi script here?  or my C lights program? $*`"

#what else do I need in this shell script.?

cat - << \END
echo Content-type: text/plain
echo done.
I am confused? I dont know how to write cgi scripts, do I need one to process user input to my very simple form(on/off) or all I need is a shell script that calls my C lights program?

any guidance will be helpfull
Old 04-12-2004, 09:06 PM   #2
Registered: Mar 2004
Location: Massachusetts
Distribution: Debian
Posts: 557

Rep: Reputation: 42
Here's an example perl script which handles both the job of printing the web page and running the lightsprogram. I make the assumption that your program is called lightsprogram and accepts -state, -on, and -off switches. I assume the -state switch prints "on" or "off".

This can of course be done through a shell script but perl has the nice CGI library, and I know it better.. hopefully this example is reasonably transparent anyway.

You would put this script in your cgi-bin directory and chmod +x it.

use strict;
use warnings;
use CGI ();

my $q = CGI->new();
my $current_state;
my $form_state = $q->param('state');
if (not defined $form_state or ($form_state ne 'Y' and $form_state ne 'N')) {
	my $output = `lightsprogram -state`;
	if (substr($output, 0, 2) eq 'on') {
		$current_state = 1;
	} else {
		$current_state = 0;
} elsif ($form_state eq 'Y') {
	system('lightsprogram -on');
	$current_state = 1;
} else {
	system('lightsprogram -off');
	$current_state = 0;

my $onoff_word = $current_state ? "ON" : "OFF";
my $on_checked = $current_state ? "checked" : "";
my $off_checked = $current_state ? "" : "checked";
print $q->header, qq(
	<h1>Lights are now $onoff_word</h1>
	<form action="lights.cgi" method=GET>
	  <input type=radio name=state value=y $on_checked />Lights ON<br />
	  <input type=radio name=state value=n $off_checked />Lights OFF<br />
	  <input type=submit value=Send />
Old 04-12-2004, 10:38 PM   #3
LQ Newbie
Registered: Sep 2003
Location: Canada
Distribution: Fedora & Gentoo-uClinux
Posts: 15

Original Poster
Rep: Reputation: 0
Hey thanks for the help, nice job on the script but I cant use perl scripts(sorry), boa doesnt support it, I have to use either unix shell scripts or C programming scripts.

I dont need the results sent back to the web page, all I need is the user imput to activate or call my C program. C lights program


Last edited by GridX; 04-12-2004 at 10:48 PM.


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