mjhjmtu

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?

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.