Shell Programming and Scripting

I am working on an embedded linux router and trying to make a webpage where the user can input a desired number of CPE and have a script update that number on the router. I have a CLI where I can log in and type the following to change that number

echo "20">/proc/net/dbrctl/maxcpe which then sets the MaxCPE at 20

Here is the code for the webpage that I am using to test this

And here is the script that it is calling
It does not work and I am confused as to why or what I need to change. I am trying to set the webpage up to either select a number from a list like I have setup there or to have an input box, and then have that number passed into the script and have it execute as if I had typed in the string in the command line interface

So if I put let's say 4 into the input box then click the button it would be as if I was in the console/command line and typed
echo "4">/proc/net/dbrctl/maxcpe

The number has to keep the quotes around it but how do I get the number I put in the webpage placed into a variable named something like cpe and then have that number in that variable echoed like above.

When I ran this in a webpage it would output cpe.sh?cpe=20 if I select 20 but ti would not update the actual number of CPE passed to /proc/net/dbrctl/maxcpe

Thanks for any help guys, I am new to this and feel lost.

Sorry, I am on my mobile phone at McDonalds having some fast road trip food so maybe I missed something....

Are you sure your webserver can write to your /proc filesystem?

If so, is that really what you want to do, from a security perspective?

I am just trying to get the webpage to call the script or pass the variable to the script and execute it just from inputting a number and clicking a button in the webpage.

Yes I am sure about the security aspect of this

Also I made a script right on the router called cpe.sh with one line:

echo "19">/proc/net/dbrctl/maxcpe

just to test it and then I ran it right on the router and it wrote 19 into the maxcpe just fine. The only problem I guess is how to properly read the input from a user and then have it passed to the script and executed properly like the above script but put the users input in place of the 19. Any suggestions?

Did you try:

Code:

#!/bin/sh
echo "$cpe">/proc/net/dbrctl/maxcpe

or

Code:

echo $cpe>/proc/net/dbrctl/maxcpe

What will you get, if you run:

Code:

echo $cpe

The information in the form is passed to the script in the variable $QUERY_STRING.

You need to parse that string to extract the variable names and values.

I use this function:

Code:

parse_query() ## probably requires bash
{
    local var val
    local IFS='&'
    unset $*
    vars="&$*&"
    [ "$REQUEST_METHOD" = "POST" ] && read QUERY_STRING
    set -f
    for item in $QUERY_STRING
    do
      var=${item%%=*}
      val=${item#*=}
      val=${val//+/ }
      case $vars in
	  *"&$var&"* )
              case $val in
                  *%[0-9a-fA-F][0-9a-fA-F]*)
                       val=$( printf "%b." "${val//\%/\\x}" )
                       val=${val%.}
              esac
              eval "$var=\$val"
              ;;
      esac
    done
    set +f
}

I call it with the names of the variables I want set, e.g.:

Code:

parse_query cpe

One obvious problem is that when you test the script from the command line, you are not running with the same userid as your web server is running. To write to the proc file system, you must be root (technically, UID 0).

It is highly unlikely your web server is running as root (it should not be, and never is); hence you cannot just pass a variable via your web server and write to the proc file system.

What is the userid you are using when you test from the command line?

Are you running Apache? What is the userid of the web server when it runs?