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Old 06-24-2010, 10:37 AM   #1
MichaelG67
LQ Newbie
 
Registered: Jun 2010
Posts: 3

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In BASH shell, how do I export a variable from a script.


Hello.

I have read several threads on this already, but none of the solutions work for me or apply to my situation.

I need to be able to set a variable that is used by my build environment. I need to be able to change this variable "on the fly" as I work with multiple build environments. A portion of the variable is arbitrary, so I need to treat the arbitrary portion of the variable as an argument.

I would normally just create an alias, but BASH doesn't support arguments to aliases. So the workaround for the no-alias-arguments bug is to use a script. No problem. Except the variable I set in the script does not exist when I exit the script.

Now, if I run the script by using "$ . myscript" it works in that the variable is set after it exits. The problem is the argument checking I have in the script doesn't work anymore.

BASH aliases don't support arguments and I can't export a variable from a script unless I source the script (is it even a script at that point?) Maybe I am simply taking the wrong approach. So I am open to other approaches to solving the original problem (should of changing my build environment of course).

Thanks
 
Old 06-24-2010, 11:31 AM   #2
David the H.
Bash Guru
 
Registered: Jun 2004
Location: Osaka, Japan
Distribution: Debian sid + kde 3.5 & 4.4
Posts: 6,823

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There is no way to directly set a variable in a shell from a script. Commands can only affect the current shell or subshells below it. Your only options are to set it in the shell itself or source it from a file.

And no, you can't arguments in aliases, but you can use them in shell functions. So one thing you can do is create a function like this, place it in your bashrc or other sourced file, and you'll have the ability to set the variable on the fly.

Code:
function setvar {
	export MYVAR="$1"
}
Edit: by the way, I personally use a similar function to "turn on" and off a set of scripts that I have by modifying the PATH variable on the fly. It works like a charm.

Code:
myscripts ()
{
    pathadd="$HOME/my_scripts";
    case $1 in
        on)
            [[ $PATH =~ $pathadd ]] || export PATH="${PATH}:$pathadd"
        ;;
        off)
            export PATH="${PATH//:$pathadd/}"
        ;;
    esac
}

Last edited by David the H.; 06-24-2010 at 11:37 AM.
 
1 members found this post helpful.
Old 06-24-2010, 02:03 PM   #3
MichaelG67
LQ Newbie
 
Registered: Jun 2010
Posts: 3

Original Poster
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That was it. I had the wrong approach. A function was the way to go. Thank you David_the_H.

Last edited by MichaelG67; 06-25-2010 at 06:06 AM.
 
  


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