What's the difference between .bashrc, .bash_profile, and .environment?

Question

I've used a number of different *nix-based systems of the years, and it seems like every flavor of Bash I use has a different algorithm for deciding which startup scripts to run. For the purposes of tasks like setting up environment variables and aliases and printing startup messages (e.g. MOTDs), which startup script is the appropriate place to do these?

What's the difference between putting things in .bashrc, .bash_profile, and .environment? I've also seen other files such as .login, .bash_login, and .profile; are these ever relevant? What are the differences in which ones get run when logging in physically, logging in remotely via ssh, and opening a new terminal window? Are there any significant differences across platforms (including Mac OS X (and its Terminal.app) and Cygwin Bash)?

Answer 1

I found information about .bashrc and .bash_profile here to sum it up:

.bash_profile is executed when you login. Stuff you put in there might be your PATH and other important environment variables.

.bashrc is used for non login shells. I'm not sure what that means. I know that RedHat executes it everytime you start another shell (su to this user or simply calling bash again) You might want to put aliases in there but again I am not sure what that means. I simply ignore it myself.

.profile is the equivalent of .bash_profile for the root. I think the name is changed to let other shells (csh, sh, tcsh) use it as well. (you don't need one as a user)

There is also .bash_logout wich executes at, yeah good guess...logout. You might want to stop deamons or even make a little housekeeping . You can also add "clear" there if you want to clear the screen when you log out.

Also there is a complete follow up on each of the configurations files here

These are probably even distro.-dependant, not all distros choose to have each configuraton with them and some have even more. But when they have the same name, they usualy include the same content.

Answer 2

A good place to look at is the man page of bash. Here's an online version. Look for "INVOCATION" section.

Answer 3

Classically, ~/.profile is used by Bourne Shell, and is probably supported by Bash as a legacy measure. Again, ~/.login and ~/.cshrc were used by C Shell - I'm not sure that Bash uses them at all.

The ~/.bash_profile would be used once, at login. The ~/.bashrc script is read every time a shell is started. This is analogous to /.cshrc for C Shell.

One consequence is that stuff in ~/.bashrc should be as lightweight (minimal) as possible to reduce the overhead when starting a non-login shell.

I believe the ~/.environment file is a compatibility file for Korn Shell.

Answer 4

The main difference with shell config files is that some are only read by "login" shells (eg. when you login from another host, or login at the text console of a local unix machine). these are the ones called, say, .login or .profile or .zlogin (depending on which shell you're using).

Then you have config files that are read by "interactive" shells (as in, ones connected to a terminal (or pseudo-terminal in the case of, say, a terminal emulator running under a windowing system). these are the ones with names like .bashrc, .tcshrc, .zshrc, etc.

bash complicates this in that .bashrc is only read by interactive but also non-login shells, so you'll find most people end up telling their .bash_profile to also read .bashrc with something like

[[ -r ~/.bashrc ]] && . ~/.bashrc

Other shells behave differently - eg with zsh, .zshrc is always read for an interactive shell, whether it's a login one or not.

The manual page for bash explains the circumstances under which each file is read. Yes, behaviour is generally consistent between machines.

.profile is simply the login script filename originally used by /bin/sh. bash, being generally backwards-compatible with /bin/sh, will read .profile if one exists.

Answer 5

That's simple. It's explained in man bash:

/bin/bash
       The bash executable
/etc/profile
       The systemwide initialization file, executed for login shells
~/.bash_profile
       The personal initialization file, executed for login shells
~/.bashrc
       The individual per-interactive-shell startup file
~/.bash_logout
       The individual login shell cleanup file, executed when a login shell exits
~/.inputrc
       Individual readline initialization file

Login shells are the ones that are read one you login (so, they are not executed when merely starting up xterm, for example). There are other ways to login. For example using an X display manager. Those have other ways to read and export environment variables at login time.

Also read the INVOCATION chapter in the manual. It says "The following paragraphs describe how bash executes its startup files.", i think that's a spot-on :) It explains what an "interactive" shell is too.

Bash does not know about .environment. I suspect that's a file of your distribution, to set environment variables independent of the shell that you drive.