I would like to create a web interface for controlling my home automation, using uHTTPd and Lua, without interfering with LuCI operation.
After reading a lot of documentation and after several trial and error, I was able to write a skeleton, solving the main difficulties.
As I don't encounter any complete example, I would like to share this one, with a double goal:
- help beginners like me (so with a very basic level :-),
- have the opinion and possible corrections or suggestions of the experts.
Files are divided into three folders:
Folder /www/
This is where index.html is, the fist file called when invoking LuCI with http:/192.168.1.1
So we have to choose an other name, say test.html and we will invoke our interface by http:/192.168.1.1/test.html
This file is almost identical to index.html
File /www/test.html
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" />
<meta http-equiv="refresh" content="0; URL=cgi-bin/test/test/" />
</head>
<body style="background-color: white">
<a href="cgi-bin/test/test/">Test</a>
</body>
</html>
Folder /www/cgi-bin/test/
Path to cgi, as defined in uHTTPd configuration, is /www/cgi-bin/ .
As I want to separate my files from those of LuCI, I create this new subfolder.
File test, called by test.html, is in this folder.
It is a simple menu offering links to the other two pages. One visualizes the current environment of uHTTPd. The other show how to get the variables passed by a GET
File /www/cgi-bin/test/test
#!/usr/bin/lua
local util = require "test/testutil"
print ("Content-type: Text/html\n\r")
util.printFile( 'test-top' )
print( '<h2>Test Menu</h2>' )
print( '<div>' )
print( '<p><a href="/cgi-bin/test/testget/">' )
print( 'Get current environment table</a></p>' )
print( '<p><a href="/cgi-bin/test/testgetqs/?var1=one&var2=two">' )
print( 'Get query string</a></p>' )
print( '</div>' )
util.printFile( 'test-bottom' )
File /www/cgi-bin/test/testget
#!/usr/bin/lua
local util = require "test/testutil"
nixio = require "nixio"
print ("Content-type: Text/html\n\r")
util.printFile( 'test-top' )
print( '<h2>Get the current environment table</h2>' )
print( '<a href="/cgi-bin/test/test/">Back to menu</a>' )
local envtable = nixio.getenv()
for k,v in pairs( envtable ) do
print( '<p>'..k..' : '..v..'</p>' )
end
print( '<a href="/cgi-bin/test/test/">Back to menu</a>' )
util.printFile( 'test-bottom' )
File /www/cgi-bin/test/testgetqs
#!/usr/bin/lua
local util = require "test/testutil"
nixio = require "nixio"
print ("Content-type: Text/html\n\r")
util.printFile( 'test-top' )
print( '<h2>Get the current query string</h2>' )
local query = nixio.getenv( 'QUERY_STRING' )
print( '<p>QUERY_STRING : "' .. query .. '"</p>' )
print( '<p>Value of var1 : "' .. util.getValQuery( 'var1' ) .. '"</p>' )
print( '<p>Value of var2 : "' .. util.getValQuery( 'var2' ) .. '"</p>' )
print( '<p>Value of var3 : "' .. util.getValQuery( 'var3' ) .. '"</p>' )
print( '<a href="/cgi-bin/test/test/">Back to menu</a>' )
util.printFile( 'test-bottom' )
Folder /usr/lib/lua/test/
Folder /usr/lib/lua/ is one of the folders where are stored lua's modules.
For the same reason as before, I create a subfolder where will be stored my modules and other files.
Module testutil.lua include two functions:
- testutil.printFile used to print common parts of web pages. They are stored in files test-top and test-bottom and include html and ccs code.
- testutil.getValQuery used to extract the value of a variable (used in testgetqs)
File /usr/lib/lua/test/testutil.lua
local testutil = {}
local io = require "io"
local nixio = require "nixio"
-- print file 'filename' located in the same folder /usr/lib/lua/test/
testutil.printFile = function( filename )
local f = io.open( '/usr/lib/lua/test/' .. filename, "r" )
if f == nil then
print( "<p>Can't open " .. filename .. "</p>" )
else
local line = f:read()
while line ~= nil do
print( line )
line = f:read()
end
f:close()
end
end
-- Get the value of a query variable 'varname'
testutil.getValQuery = function( varname )
local value
local query = nixio.getenv( 'QUERY_STRING' )
if query ~= nil then
query = '&' .. query
varname = '&' .. varname .. '='
local p, q = string.find( query, varname )
if q ~= nil then
p = string.find( query, '&', q )
if p == nil then p = -1 else p = p - 1 end
value = string.sub( query, q + 1, p )
end
end
value = value or 'No such variable'
return value
end
return testutil
File /usr/lib/lua/test/test-top
<html>
<head>
<style rel='stylesheet' type='text/css'>
body {
background-color: Beige; color: DarkGreen;
font-family:'DejaVu Sans', Helvetica, sans-serif;
}
h1 { font-size:6vh; text-align:center; color: Navy; }
h2 { font-size:4vh; text-align:center; color: Navy; }
</style>
<title>An example</title>
<meta charset="utf-8">
</head>
<body>
<h1>Example of using Lua under uhttpd</h1>
File /usr/lib/lua/test/test-bottom
<p style='font-size:4vh; text-align:center; color: Navy;'>
by J-M Gallego
</p>
</body>
</html>
After copying this files in they respective folders and if you have LuCI installed, you must be able to test them, without loading any additional software.
As usual, comments, critics and corrections are welcome!
In particular, I wonder if:
- would it be possible to have only one folder for cgi and lua files?
- If there is a need to store data, which folder should I use? /root ? , /tmp ?
