how can i change the value of a environment variable through shell script ?

manomohan · 02-08-2010, 07:17 AM

Hi

i have created a environment variable in .bash_rc file.

eg: PDL_VALUE= TRUE

is it possible to change the value of the above variable through a shell script.

if not, have any alternative way to change.

Actually my need to set a status of job (periodic checking) thru the variable and use that variable in another script.

David the H. · 02-08-2010, 07:25 AM

No, it's not possible to set anything in the environment above whatever command is running. To be able to do so would be a big security risk.

The only real way I know of to set your environment through a script is to have it sourced by your start-up script, which in essence makes it part of that start-up script.

To transfer information between scripts you need to use a temporary file or perhaps a fifo.

manomohan · 02-10-2010, 06:37 AM

I tried with file.

I kept the variable in a file and sourcing this file wherever i need.
And updating the value in the file

#!/bin/bash
. valuevar
echo $PDL_STATUS

if [ $PDL_STATUS = 'TRUE' ]
then
sed -e 's/FALSE/TRUE/' valuevar > newfile
mv -f newfile valuevar
else
sed -e 's/TRUE/FALSE/' valuevar > newfile
mv -f newfile valuevar
fi

manomohan · 02-10-2010, 06:41 AM

And my next requirement is to start another script (script B) in true condition. At the same time i need to exit from the current script (above mentioned script)

Which is the good way 2 do that.

David the H. · 02-10-2010, 03:46 PM

Sourcing the file back into your first script does no good. All it does is set the environment of that script, meaning it's still unavailable outside of it. In order to set the environment of the shell, it needs to be sourced by the shell itself.

Or, since your purpose is to set the environment of the second script, export it to a file with the first script, then source that file into the second script.

manomohan · 02-10-2010, 11:05 PM

Can you just elaborate on the above solution.

Actually the content in the file valuevar is given below,

PDL_SATUS='TRUE'
export PDL_STATUS;

jschiwal · 02-10-2010, 11:10 PM

Export the variables you define in .bashrc. The file is sourced so it doesn't run in a subshell. Export moves variables from normal memory to environmental memory.

In your first post, you had a space after the equals sign. You would be clearing the variable instead and then running the true command.

If you intend for .bash_rc to be used only in certain scripts, then source .bash_rc in the beginning of the scripts that use it.

chrism01 · 02-10-2010, 11:50 PM

Quote:

PDL_SATUS='TRUE'
export PDL_STATUS;

There's a typo there ... hope its not in the real file ...

manomohan · 02-11-2010, 09:55 PM

The typo error is only for here..
Thanks for pointing out that..