During Shell scripting, we may need a few variables, which cannot be modified. This may be needed for security reasons. We can declare variables as read-only using following command read-only:
The usage is as follows:
$ readonly currency=Dollars
Let's try to remove the variable:
$ unset currency bash: unset: currency: cannot unset: readonly variable
If we try to change or remove the ready-only variable in the script, it will give the following error:
#!/bin/bash AUTHOR="Ganesh Naik" readonly AUTHOR AUTHOR="John"
This would produce the following result:
/bin/sh: AUTHOR: This variable is read only.
Another technique:
Declare -r variable=1 echo "variable=$variable" (( var1++ ))
Output after execution of the script:
line 4: variable: readonly variable