help needed for converting strings in a file

[Sourabh Bora <sourabhbora@gmail.com>]

hi,,

        i am making a small tool for
offline web browsing.. For this I need to change the source of html files.
   let me explain::
 
        In a web page the hyper links are written as

href="http://www.micronux.com/catalog/"

      i want this particular string to convert to 


href="./micronux.com_catalog"
      
      The logic is --1)delete 
http://www.  
                      2) replace '/' '?' etc with '_'

     I want to write a script using sed or awk which will do all the conversion in a file..
Any help in this regard will be highly appreciated..
         Thanking you
Sourabh Bora
Symbol Technologies India Ltd
Bangalore 
India

   
  Once I cross this stage I plan to make furthur improvements to make a user friendly offline browser.
PS:
 I have written a C program but,,,it is very limited in functionality.
Usage:
     ./a.out "
http://www.micronux.com/catalog/"
output is
    micronux.com_catalog
The limitation is it cannot search the whole file for any url starting with href=


The code::::::
int  main(int argc,char * *argv) {

        char url[200];
        char output[200];
        int urlCount;
        int outputCount;
        strcpy(url,argv[1]);
        urlCount=4;//start with url[4]--if http its : if https its "s"

        if (url[urlCount]==':')
                urlCount=7;
        else
                urlCount=8;

        //now check for "www."
        if(url[urlCount]=='w' && url[urlCount+1]=='w'&& url[urlCount+2]=='w' && url[urlCount+3]=='.')

                urlCount+=4;
        //now do the actual conversion--convert / \= : * ?" <> and | to _

        for (outputCount=0;url[urlCount]!='\0';urlCount++,outputCount++){

                if(url[urlCount]=='/' || url[urlCount]== '\\' || url[urlCount]=='=' || url[urlCount]==':' || url[urlCoun
t]=='*' || url[urlCount]=='\"' || url[urlCount]=='?' || url[urlCount]=='<' || url[urlCount]=='>' || url[urlCount]=='|')

                        output[outputCount]='_';
                else
                        output[outputCount]=url[urlCount];

        }

        outputCount--;

//if the last character is '-' remove it

if(output[outputCount]=='_')
        output[outputCount]='\0';
else
        output[++outputCount]='\0';
printf("%s\n",output )  ;
return 0;
}