First attempt: local readonly var1
That is the way I used to define it. It is wrong. I will define my variable var1 as local, but it will not be readonly, as you can see on example below, I can change the value of var1, and I don’t want that!
:~$ (
> myfunction()
> {
> # Define variable
> local readonly var1="val1"
>
> echo "Readonly output:"
> readonly | grep -E 'readonly|local|var1'
> echo ""
>
> echo "Local output:"
> local | grep -E 'readonly|local|var1'
> echo ""
>
> var1="val2"
> echo "VAR1 INSIDE: ${var1}"
> }
> myfunction
> echo "VAR1 OUTSIDE: ${var1}"
> )
Readonly output:
Local output:
var1=val1
VAR1 INSIDE: val2
VAR1 OUTSIDE:
Second attempt: readonly local var1
This time it will define var1 as readonly, but it will also define a variable called local, so using this way it will not handle local as keyword, it will be a variable name.
Check also that the scope of var1 is not local, in fact it is global, we can see the value of var1 outside the function.
:~$ (
> myfunction()
> {
> # Define variable
> readonly local var1="val1"
>
> echo "Readonly output:"
> readonly | grep -E 'readonly|local|var1'
> echo ""
>
> echo "Local output:"
> local | grep -E 'readonly|local|var1'
> echo ""
>
> echo "VAR1 INSIDE: ${var1}"
> }
> myfunction
> echo "VAR1 OUTSIDE: ${var1}"
> )
Readonly output:
declare -r local
declare -r var1="val1"
Local output:
VAR1 INSIDE: val1
VAR1 OUTSIDE: val1
As it should be: local -r var1
This way it will do exactly what I want, it will define var1 as scope local AND readonly.
:~$ (
> myfunction()
> {
> # Define variable
> local -r var1="val1"
>
> echo "Readonly output:"
> readonly | grep -E 'readonly|local|var1'
> echo ""
>
> echo "Local output:"
> local | grep -E 'readonly|local|var1'
> echo ""
>
> #var1="val2"
> echo "VAR1 INSIDE: ${var1}"
> }
> myfunction
> echo "VAR1 OUTSIDE: ${var1}"
> )
Readonly output:
declare -r var1="val1"
Local output:
var1=val1
VAR1 INSIDE: val1
VAR1 OUTSIDE:
We can define it as below also, but one line is better than two!
local var1="val1"
readonly var1