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I need to change variable name every time I ran script. Lets say I have a variable

a="foo"
echo "Value is : $a"

and it will print

Value is foo

But in same script i am changing the variable value

a="bar"

And if i run the script again it should print

Value is bar

Can we achieve that in unix?

  • Have you tried it? What happened? – roaima Feb 1 at 7:19
2

The line $a="bar" ought to give you an error message saying

bash: foo=bar: command not found

To set a to the string bar, use a="bar". Notice that $a is the value of the variable a, and that $a="bar" is nonsensical.

If you want to change the value each time you run the script, you can do two things (at least).

  1. Make a an environment variable. This mean that you set a outside of the script and export it:

    export a="bar"
    

    Then you run your script as usual (it would need to be modified to not overwrite the value of a inherited from the environment first). You could also use

    a="bar" ./myscript.sh
    

    to set the variable for the script only (i.e., not making it a variable in the calling shell).

  2. Make the script take the value from the command line, so that you call the script like

    ./myscript.sh "bar"
    

    The script would then do

    a="$1"
    

    to set the value of a from the command line argument. Here, $1 means "the first command line argument".

Whichever way you go about doing this, you may also want to check that the value "$a" is sane (i.e. contains valid data) before using it.

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