LinuxQuestions.org - confusion about permanent env variables

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

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

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! :)