Network Proxy Settings

[cmanL]

Is there a way to change the network proxy settings from a C program that runs in a terminal window? I know the environment variables for HTTP proxies can be changed with the command:

      export http_proxy=http://MyProxy:MyPortNumber

and I know the gclib provides a function in stdlib.h ,

      setenv ( const char * name , const char * value , int overwrite )

that can be used to change environment variables in a shell. Could one write a command line application to change proxy settings of Mozilla Firefox by using the above information ( I know that it would probably be better to write such an application using the Mozilla programming framework , but I haven't learned enough about programming Mozilla yet - I'm reading Programming Firefox currently ). Also , does anyone know of a good book on programming the X-Windows system? I've been programming Microsoft Windows for a number of years , but have no knowledge of the Linux GUI system. Thanks for any information!

[cmanL]

I guess setting the environment variables to spawn a new process ( firefox ) with a certain proxy setting would only work one time ( the child process's copy of the environment variables would not change with the parent process's variable changes after the initial fork of the child process ). Anyway , I've been reading Volume One: Xlib Programming Manual for Version 11 of the X-Window System by O'Reilly Press to learn X-Windows programming with the C/C++ programming language. Is this book still up to date? I hear this is one of the only good books available to learn such programming. Thanks for any input.....