Question

for every successful login, which script will be executed?

Answer 1

The answer is Profile.

Answer 2

The answer is /etc/profile.

For every successful login, the /etc/profile script will be executed.

This script encompasses Linux system startup programs and wide environment. Any user with sh, bash or ksh shells can execute this script that works only for login shell.  

The /etc/profile script can be used to set parameters such as user limits and PATH variables.