Tuesday, November 30, 2010

About .bashrc .bash_profile .profile .bash_login and /etc/profile

Have you ever wondered what is the purpose of ~/.bashrc ~/.bash_profile ~/.bash_login ~/.profile and /etc/profile files in Linux.

Bash is the default shell on most of the Linux distributions like Fedora and Ubuntu. If you take a look at man pages for Bash, you will get the following explanation:
When bash is invoked as an interactive login shell, or as a  non-interactive  shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable.  
When  an  interactive shell that is not a login shell is started, bash reads and executes commands from ~/.bashrc, if that file exist. 
Interactive shell is the one which is not running because of a script and lets you enter commands to interact with it. Login shell is the one where you are asked for user name and password before you can enter commands. An example of an interactive login shell is the one that you get after you login to a system using ssh. An example of non-login interactive shell is a shell that you get when you run terminal from menu item or some icon.

So when you login to a Linux system, first commands from /etc/profile (if it exists) will get executed. Then the system will look for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and execute commands from the first of these files that it founds. And when you open Konsole/Terminal from KDE or GDM, first commands from /etc/bash.bashrc (if it exists) will get executed and then commands from ~/.bashrc (if it exists) will get executed.

So if you want to execute a command for all users then you will need to add it to /etc/profile but if you want a command executed for a specific user then you can add it to .profile, .bash_profile, .bash_login or .bashrc in his/her home directory.

Please keep in mind that KDE and GDM are not login shells so there behavior is different. I dont know about KDE but GDM first executes command from /etc/profile and then from ~/.profile.

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