Linux: where are environment variables stored?
LinuxEnvironment VariablesLinux Problem Overview
If I type into a terminal,
export DISPLAY=:0.0
... where is the shell storing that environment variable?
I'm using Ubuntu 8.10. I've looked in the files ~/.profile and /etc/profile and can find no trace of DISPLAY.
Linux Solutions
Solution 1 - Linux
The environment variables of a process exist at runtime, and are not stored in some file or so. They are stored in the process's own memory (that's where they are found to pass on to children). But there is a virtual file in
/proc/pid/environ
This file shows all the environment variables that were passed when calling the process (unless the process overwrote that part of its memory — most programs don't). The kernel makes them visible through that virtual file. One can list them. For example to view the variables of process 3940, one can do
cat /proc/3940/environ | tr '\0' '\n'
Each variable is delimited by a binary zero from the next one. tr replaces the zero into a newline.
Solution 2 - Linux
Type set and you will get a list of all the current variables.
If you want something to persist put it in ~/.bashrc or ~/.bash_profile (if you're using bash)
Solution 3 - Linux
If you want to put the environment for system-wide use you can do so with /etc/environment file.
Solution 4 - Linux
It's stored in the process (shell) and since you've exported it, any processes that process spawns.
Doing the above doesn't store it anywhere in the filesystem like /etc/profile. You have to put it there explicitly for that to happen.
Solution 5 - Linux
There is 1 file that can be used to store env variables.
> .bashrc
You can add your variables and use them. For example I have added Django virtual env as environment variable and now I can access it anywhere. Add this to your bashrc file
django_env='source/media/anish/Softwares/virtual_env/django2/bin/activate'
now you need to restart your system to reflect changes and after restarting enter $django_env to start your virtual environment. as simple as that.
Solution 6 - Linux
As to the location of environment variables in RAM, they are stored in the top of the stack of main() function. any dynamic modification by setenv() et al. are then allocated elsewhere
Solution 7 - Linux
That variable isn't stored in some script. It's simply set by the X server scripts. You can check the environment variables currently set using set.