Subject: Tech Republic article
From: Mike Barsalou (mbarsalou@aidea.org)
Date: Fri Nov 09 2001 - 10:07:27 AKST
Here is a great little article I found on Tech Republic. If you aren't
already registered there, you should seriously consider it:
Today's Linux tip
UNDERSTANDING BASH STARTUP FILES
The bash shell uses a variety of startup files, which are roughly
analogous to the Autoexec.bat file on MS-DOS systems. What confuses
more than a few Linux users is that bash (unlike MS-DOS) uses more than
one startup file. Often, bash users have trouble figuring out which
file they should use for new, automatically executed commands.
Here's a quick review of the startup files that bash can use, followed
by a discussion of just when these startup files come into play. Note
that the tilde (~) stands for your home directory.
The /etc/profile is the main startup file for bash. Because it is
located in the /etc directory, which should be readable for all system
users, it is used for commands that all users need. In contrast, a
user's home directory contains one or more of the following bash
startup files, which contain commands that apply only to the current
user's bash session: ~/.bash_profile, ~/.bash_login, ~/.profile,
~/bash_rc, and ~/.bash_logout.
To understand how bash employs the various user startup files, you must
understand the difference between a login shell and a nonlogin shell. A
login shell is created when you log in to your Linux account. A
nonlogin shell is created when you launch an additional bash shell
within your user session, as you do when you open a terminal window in
X.
When you start a login shell, bash consults the following files in the
specified order:
1. /etc/profile
2. ~/.bash.profile
3. ~/.bash_login
4. ~/.profile
When you start a nonlogin shell, bash consults only one startup file,
~/bash.rc.
Because login and nonlogin shells use different startup files, both
shells may differ. Most Linux distributions contain an automatically
generated ~./bash_profile that contains a script that automatically
executes the commands placed in ~/bash_rc. This script ensures that the
login shell will be configured like the nonlogin shell. Although this
script is useful, a full understanding of the way bash works with
startup files is needed if you wish to understand just where you should
add commands to a bash startup file.
To add a command that is automatically executed when any user begins a
login shell, add the command to /etc/profile. You'll need to switch to
superuser status to edit this file.
To add a command that is executed when you start a login shell in your
own user account, use ~/bash.profile for commands that must be executed
before commands contained in ~/.bash_login or ~/profile. Use ~/.profile
for commands that must be executed only after the shell executes the
commands found in ~/.bash.profile and ~/bash_login.
To add a command that is executed when you start a nonlogin shell, use
~/.bashrc.
This archive was generated by hypermail 2a23 : Fri Nov 09 2001 - 10:15:28 AKST