1. update the user's profile, normaly it is in /home/user_name/.profile, add the program at the end of the file followed by 'exit' statement.
(Warning: You have to make sure turn off the signals, etc TERM, KILL, otherwise someone can
hacked it),
It is not a very safy way, but convenient.
2. change the /etc/passwd file, change the default shell to you program.
But this way you have to provide user/passwd verification by you self and deal with other issues, like make it a standalone process, response to the TTY lines,...
it is more safe than the first
3. hack the login program in Linux/Unix.
change the default login program, make it pass the control to you program after it finishs its work.
this is the most saftest way, and more difficult. Unless the security is the most important for you,
do not try this.
(Warning: You have to make sure turn off the signals, etc TERM, KILL, otherwise someone can
hacked it),
It is not a very safy way, but convenient.
2. change the /etc/passwd file, change the default shell to you program.
But this way you have to provide user/passwd verification by you self and deal with other issues, like make it a standalone process, response to the TTY lines,...
it is more safe than the first
3. hack the login program in Linux/Unix.
change the default login program, make it pass the control to you program after it finishs its work.
this is the most saftest way, and more difficult. Unless the security is the most important for you,
do not try this.