Any other way to define an environment variable?

Question

I'm quite new to Linux. Debian Wheezy is now running on my Laptop (64 bits).

I recently installed Oracle 11g R2 database for evaluation purpose, and defined environment variables (such as ORACLE_SID) through a script /etc/profile.d/oracle.sh. This works fine, but for the "oracle" user.

I change user by su - oracle.
The value of ORACLE_SID is different from the one specified in the /etc/profile.d/oracle.sh file. As the oracle user has no file (such as .bash_profile, .profile etc.) in its home directory, where can this value come from?

What is the overloading sequence of environment variables?

Answer 1

What ever set's the environment variable last wins. So it doesn't really matter, I would just set the variable in the oracle user's $HOME/.bashrc file towards the bottom.

The file $HOME/.bashrc is the key file which sources files such as /etc/bashrc and the files under /etc/profile.d/*.sh for example. So I would just set ORACLE_SID=whatever in $HOME/.bashrc.

Debugging Tip

If you want to see what's going on you can debug your login like so:

su - oracle -c "env SHELLOPTS=xtrace bash"

With the above command you can follow along as the different files are sourced by bash:

...
...
++ for i in '/etc/profile.d/*.sh'
++ '[' -r /etc/profile.d/less.sh ']'
++ '[' '[\u@\h \W]\$ ' ']'
++ . /etc/profile.d/less.sh
+++ '[' -x /usr/bin/lesspipe.sh ']'
+++ export 'LESSOPEN=||/usr/bin/lesspipe.sh %s'
+++ LESSOPEN='||/usr/bin/lesspipe.sh %s'
++ for i in '/etc/profile.d/*.sh'
++ '[' -r /etc/profile.d/PackageKit.sh ']'
++ '[' '[\u@\h \W]\$ ' ']'
++ . /etc/profile.d/PackageKit.sh
++ for i in '/etc/profile.d/*.sh'
++ '[' -r /etc/profile.d/qt.sh ']'
++ '[' '[\u@\h \W]\$ ' ']'
++ . /etc/profile.d/qt.sh
+++ '[' -z /usr/lib64/qt-3.3 ']'
++ for i in '/etc/profile.d/*.sh'
++ '[' -r /etc/profile.d/udisks-bash-completion.sh ']'
++ '[' '[\u@\h \W]\$ ' ']'
++ . /etc/profile.d/udisks-bash-completion.sh
+++ '[' -z '4.1.7(1)-release' ']'
+++ complete -o filenames -F __udisks udisks
++ for i in '/etc/profile.d/*.sh'
++ '[' -r /etc/profile.d/vim.sh ']'
++ '[' '[\u@\h \W]\$ ' ']'
++ . /etc/profile.d/vim.sh
+++ '[' -n '4.1.7(1)-release' -o -n '' -o -n '' ']'
+++ '[' -x //usr/bin/id ']'
++++ //usr/bin/id -u
+++ '[' 0 -le 200 ']'
+++ return
++ for i in '/etc/profile.d/*.sh'
++ '[' -r /etc/profile.d/which2.sh ']'
...
...