How do I delete an exported environment variable?

Question

Before installing gnuplot, I set the environment variable GNUPLOT_DRIVER_DIR = /home/gnuplot/build/src. During the installation, something went wrong.

I want to remove the GNUPLOT_DRIVER_DIR environment variable. How can I achieve it?

Solution 1

unset is the command you're looking for.

unset GNUPLOT_DRIVER_DIR

Solution 2

Walkthrough of creating and deleting an environment variable in Bash:

Test if the DUALCASE variable exists (empty output):

env | grep DUALCASE

It does not, so create the variable and export it:

DUALCASE=1
export DUALCASE

Check if it is there:

env | grep DUALCASE

Output:

DUALCASE=1

It is there. So get rid of it:

unset DUALCASE

Check if it's still there (empty output):

env | grep DUALCASE

The DUALCASE exported environment variable is deleted.

Extra commands to help clear your local and environment variables:

Unset all local variables back to default on login:

CAN="chuck norris"
set | grep CAN

Output:

CAN='chuck norris'

env | grep CAN # Empty output

exec bash
set | grep CAN
env | grep CAN # Empty output

exec bash command cleared all the local variables, but not environment variables.

Unset all environment variables back to default on login:

export DOGE="so wow"
env | grep DOGE

Output:

DOGE=so wow

env -i bash
env | grep DOGE # Empty output

env -i bash command cleared all the environment variables to default on login.

Solution 3

The original question doesn't mention how the variable was set, but:

In C shell (csh/tcsh) there are two ways to set an environment variable:

1. set x = "something"
2. setenv x "something"

The difference in the behaviour is that variables set with the setenv command are automatically exported to a subshell while variables set with set aren't.

To unset a variable set with set, use

unset x

To unset a variable set with setenv, use

unsetenv x

Note: in all the above, I assume that the variable name is 'x'.

Credits:

• TCSH / CSH: set vs setenv Command Differences

• set, unset, setenv, unsetenv, export — Shell Environment Variable Built-in Functions

Solution 4

This may also work.

export GNUPLOT_DRIVER_DIR=

Solution 5

As mentioned in the above answers, unset GNUPLOT_DRIVER_DIR should work if you have used export to set the variable. If you have set it permanently in ~/.bashrc or ~/.zshrc then simply removing it from there will work.

View more solutions

Comments

[Elijah Lynn]

For those looking for how to do this in Fish shell see stackoverflow.com/questions/30703860/… (even though this question isn't for a specific shell)

[eLRuLL]

but this only works for a session, what about unsetting it definitely? or maybe searching where is the variable set, so you can go and delete it?

[matt5784]

This should work per terminal instance. Generally, each time a terminal window is opened, it will load up variables from various places such as ~/.bashrc, ~/.profile, etc. Any variables you set in one terminal instance will not carry over to another. If you have a variable which seems to be set automatically every time you open terminal, try looking through the various hidden files in your home directory for it. Or, to see where it is being set, try "grep -r <X> ~" where <X> is the name of the variable. This may take a while if you have a lot of files in your home directory.

[Rodrigo Gurgel]

maybe echo $VARIABLE is better than env | grep VARIABLE, it's lighter as it doesn't need to print all variables and then send its output to another (grep) process. Plus, env | VARIABLE could catch more than one variable that matches the same pattern. Plus2, echo $VARIABLE makes possible to complete variable's name by hitting <Tab> (if it exists, that also may be a hint to what you wanna do).

[calasyr]

'env | grep VARIABLE' is better than 'echo $VARIABLE' because I can tell it's truly gone

[hmijail]

@RodrigoGurgel, echo $VARIABLE doesn't tell you whether the VARIABLE is a shell variable (here called "local variable") or an environment variable, which is the whole point of the walkthrough.

[olejorgenb]

This removes the variable from the shell too though. Is the only way to unexport to do T="$MYVAR"; unset MYVAR; MYVAR="$T"; unset T ?

[Peder Klingenberg]

@olejorgenb At least in bash, you can say declare +x MYVAR to remove the export but keep the value in the current shell.

[jarno]

@PederKlingenberg export -n MYWAR works as well in Bash.

[Mark Chackerian]

Note that env -i bash seems to be creating a subshell (at least on a Mac) which may have unintended consequences.

[Palec]

The variable still exists, but it contains an empty string, as you can see in the output of the env command. It just might be the case that the application that uses the variable does not distinguish between non-existent and empty environment variable.

[Nilesh K.]

yes it will contain, this was just to remove value not to remove variable. But yes one can use - unset GNUPLOT_DRIVER_DIR.

[Thomas B in BDX]

@RodrigoGurgel using echo won't show existing variable set to empty string or nul. to your point, though, a proper way to test for variable would be env | grep -e '^VARNAME='.

[4levels]

Great addition about the differences between set / setenv wrt subshells!

[Chad]

This doesn't work in the case of the PAGER variable. I tried to unset my PAGER setting with export PAGER=, but that just disabled paging entirely--all my man pages just dumped straight to the terminal. unset PAGER did the trick, reverting it to default behaviour.

[Peter Mortensen]

Perhaps it is time to update your answer? (But without "Edit:", "Update:", or similar - the question/answer should appear as if it was written today.)