The question says it all. I currently use Arch Linux and the zsh, but I'd like a solution that (at minimum) works both on VTs and in xterms and also (hopefully, preferably) will continue to work if I switch distros or shells.
I've heard wildly disparate answers to this question in different distros' docs. Ubuntu says "use .pam_environment". I think in Arch what they recommend depends on your shell. Currently I put everything in .profile and if a shell doesn't source that for some reason (e.g. bash if .bash_profile exists), I override that by manually sourcing it. But it seems like there must be a better way.
Best Answer
There is unfortunately no fully portable location to set environment variables. The two files that come closest are
~/.profile
, which is the traditional location and works out of the box on many setups, and~/.pam_environment
, a modern, commonplace but limited alternative.What to put in
~/.pam_environment
The file
~/.pam_environment
is read by all login methods that use PAM and that have this file enabled. This covers most Linux systems nowadays.The major advantage of
~/.pam_environment
is that (when enabled) it is read before the user's shell starts, so it works regardless of the session type, login shell and other complexities. It even works for non-interactive logins such assu -c somecommand
andssh somecommand
.The major limitation of
~/.pam_environment
is that you can only put simple assignments there, not complex shell syntax. The syntax of this file is as follows.VAR=VALUE
where VAR consists of letters, digits and underscores. The alternative formVAR DEFAULT=value
allows expansions of environment variables using${VAR}
syntax and the special variables@{HOME}
and@{SHELL}
.#
starts a comment, it cannot appear in a value."
, then VAR is set to the string between the quotes.\$
or\@
insert a literal$
or@
and long lines can be split by escaping the newline with a\
.=
or unquoted whitespace, the variable is removed from the environment.So on the upside,
~/.pam_environment
works in a large array of circumstances. On the downside, you cannot use the output of a command (e.g. test if a directory or program is present), and some characters (#"
, newline) are impossible or troublesome to put in the value.What to put in
~/.profile
This file should have portable (POSIX) sh syntax. Only use ksh or bash extensions (arrays,
[[ … ]]
, etc.) if you know that your system has these shells as/bin/sh
.This file may be read by scripts in automated applications, so it should not call programs that produce any output or call
exec
. If you want to do that on text-mode logins, do it only for interactive shells. Example:This is an example of using
/bin/sh
as your login shell and switching to your favorite shell. See also how can I use bash as my login shell when my sysadmin refuses to let me change itWhen is
~/.profile
not read on non-graphical login?Different login shells read different files.
If your login shell is bash
Bash reads
~/.bash_login
or~/.bash_profile
if they exist instead of~/.profile
. Also bash does not read~/.bashrc
in a login shell even if it is interactive. To never have to remember these quirks again, create a~/.bash_profile
with the following two lines:See also Which setup files should be used for setting up environment variables with bash?
If your login shell is zsh
Zsh reads
~/.zprofile
and~/.zlogin
, but not~/.profile
. Zsh has a different syntax from sh, but can read~/.profile
in sh emulation mode. You can use this for your~/.zprofile
:See also Zsh not hitting ~/.profile
If your login shell is some other shell
There's not much you can do there, short of using
/bin/sh
as your login shell and your favorite shell (such as fish) as an interactive shell only. That's what I do with zsh. See above for an example of invoking another shell from~/.profile
.Remote commands
When invoking a remote command without going through an interactive shell, not all shells read a startup file.
Ksh reads the file specified by the
ENV
variable, if you manage to pass it.Bash reads
~/.bashrc
if it is not interactive (!) and its parent process is calledrshd
orsshd
. So you can start your~/.bashrc
withZsh always reads
~/.zshenv
when it starts. Use with caution, since this is read by every single instance of zsh, even when it is a subshell where you've set other variables. If zsh is your login shell and you want to use it to set variables only for remote commands, use a guard: set some variable in~/.profile
, such asMY_ENVIRONMENT_HAS_BEEN_SET=yes
, and check this guard before reading~/.profile
.The case of graphical logins
Many distributions, display managers and desktop environments arrange to run
~/.profile
, either by explicitly sourcing it from the startup scripts or by running a login shell.Unfortunately, there is no general method to handle distro/DM/DE combinations where
~/.profile
is not read.If you use a traditional session started by
~/.xsession
, this is the place where you should set your environment variables; do it by sourcing~/.profile
(i.e.. ~/.profile
). Note that in some setups, the desktop environment startup scripts will source~/.profile
again.