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Need a way to clear out Linux env variables

Posted on 2011-09-07
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Last Modified: 2012-05-12
I would like to delete all the environment variables in my LINUX session and then set all the env variables to a set of values I choose.

250 points for help
500 for code that does what I need. Could be Shell script, perl, c++
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Question by:Christopher Schene
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Accepted Solution

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wesly_chen earned 2000 total points
ID: 36500697
For csh/tcsh, just do
unsetenv  *


For sh/bash shell
for  VAR  in  `/usr/bin/env | egrep '^(\w+)=(.*)$' |  egrep -vw 'PWD|USER|LANG|_' | /usr/bin/cut -d= -f1`
do
   unset $VAR
done


or (one-liner)
unset `env | awk -F= '/^\w/ {print $1}' | egrep -v 'PWD|USER|LANG|_' | xargs`
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Author Comment

by:Christopher Schene
ID: 36500725
Hi Wesly,

thanks for the fast response.

Just to clarify: This only clears the env variables for the current login session, correct?

Thanks,

Chris Schene
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LVL 38

Expert Comment

by:wesly_chen
ID: 36500737
> only clears the env variables for the current login session
Yes. it only clear the current shell session.
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Expert Comment

by:svs
ID: 36502538
in bourne shells,
env -i

Open in new window

may help too
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Author Comment

by:Christopher Schene
ID: 36504137
I tried the loop before and I have uploaded the before and after env values

Is this what you would expect?

for  VAR  in  `/usr/bin/env | egrep '^(\w+)=(.*)$' |  egrep -vw 'PWD|USER|LANG|_' | /usr/bin/cut -d= -f1`
do
   unset $VAR
done

Before executing the loop

 env-before-clear.txt

After executing the loop

env-after-clear.txt
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LVL 38

Expert Comment

by:wesly_chen
ID: 36504298
The env-after looks good to me.
Any specific environment variable you don't want and it still exist?
Try manually run "unset <env variable name>" to see if you can unset or not.
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Author Comment

by:Christopher Schene
ID: 36504561
increasing points
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Author Closing Comment

by:Christopher Schene
ID: 36504566
Great solution, fast response.
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