confusion about permanent env variables

toma20082010 · 03-10-2011, 09:31 AM

hi there,

when we set an permanent environment variable we set it like this VARIABLE = WHATEVER WE WANT,
but where exactly we do that?
because i was searching for it and it was confusing.
some say in .bash_profile
or .profile
or .bashrc
and whether in /home directory or /etc directory.
im using bash shell.

thanks

corp769 · 03-10-2011, 12:18 PM

Honestly that is up to you. Are you trying to set variables before you start a bash session? You could use either .bashrc or .bash_profile; The files in your home directory would be set for only your user, and the config files in /etc are for global settings.

devUnix · 03-10-2011, 01:01 PM

Try to grasp as much of what follows here as possible:

(Temporary) Bash Variables:

varName=value
Example# 1:

Code:

-bash-2.05b# logFile=/tmp/myLog
-bash-2.05b# echo $logFile
/tmp/myLog

Example# 2:

Code:

-bash-2.05b# maxWarnings=10
-bash-2.05b# echo $maxWarnings
10

Example# 3:

Code:

-bash-2.05b# developerName="Mr. Dev"
-bash-2.05b# echo $developerName
Mr. Dev

Those variables will not be available when your script terminates or login session is closed.

Persistent Bash Variables:

export variableName=value

Example# 4:

Code:

-bash-2.05b# export greetings="Have happy working hours, ${USER}."
-bash-2.05b# echo $greetings
Have happy working hours, root.
-bash-2.05b# cat > persVar.sh
#!/bin/bash
echo $greetings
-bash-2.05b# chmod +x persVar.sh
-bash-2.05b# persVar.sh
Have happy working hours, root.

Now decide on:

You want to use a persistent variable whenever

[1] any user logins (in the present and in the future as well)
[2] or only you login

Method# 1-A

edit /etc/profile
Insert the following line at an appropriate place or at the end of the file:

Code:

export greetings="Have happy working hours, ${USER}."

Method# 1-B

Code:

-bash-2.05b# echo 'export greetings="Have happy working hours, ${USER}."' >> /etc/profile
-bash-2.05b# tail -n 1 /etc/profile
export greetings="Have happy working hours, ${USER}."

Method# 2-A

edit the file

Code:

ls -l ~/.bash_profile

OR

Code:

ls -l ~/.profile

Insert the following line at an appropriate place or at the end of the file:

export greetings="Have happy working hours, ${USER}."

Method# 2-B

Code:

-bash-2.05b# echo 'export greetings="Have happy working hours, ${USER}."' >>  ~/.bash_profile

OR

Code:

-bash-2.05b# echo 'export greetings="Have happy working hours, ${USER}."' >>  ~/.profile

Verify your work:

Code:

login as: demo
demo@linuxzoo.net's password:
[demo@host-6-41 demo]$ echo $greetings
Have happy working hours, demo.
[demo@host-6-41 demo]$

A note on .bash_profile or .profile versus .bashrc

When you login, your .bash_profile or .profile file is executed which in turn first checks whether .bashrc exists or not. If it does, then it is first called:

Code:

[demo@host-6-41 demo]$ more .bash_profile
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

That means that you can write your "permanent bash variables" in .bashrc after (preferably) "# User specific environment and startup programs" or in your .bash_profile (or .profile) file as shown earlier.

Code:

[demo@host-6-41 demo]$ more .bash_profile
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

# User specific environment and startup programs

Feel free to play with both the files, but first take their backup:

Code:

cp .bashrc .bashrc-bk
cp .profile .profile-bk

Note: If you edit .profile or .bash_profile or .bashrc then you can bring the variables to life without having to relogin:

Code:

source .bash_profile

Cheers!

business_kid · 03-10-2011, 01:03 PM

All over the place is where we set things. Some places

/etc/profile.d/*
/etc/bashrc
~/.bash_profile
~/.bashrc
files in /etc/rc.d/
/etc/environment (If it exists)
Then there's the glibc locale stuff, /etc/X11/*

But never mind that. You can fiddle the stuff yourself. The syntax is

STRANGEVAR="mad value"
export $STRANGEVAR

The favourite one is $PATH; everyone fiddles that. and with reason, because you can limit the directories that something has access to. lusers generally don't have the ~/sbin directories in their path.