You do know the result of this:
a=A; echo $a
But are you just as sure here?
a=A; b=B; echo $a.$b
That depends on the shell, you are using. So I suggest you better write it this way:
a=A; b=B; echo ${a}.${b}
Enclosing variable names in curly braces is quite often a good idea.
Look at the following piece of code:
case $var in
x*)
echo var starts with x
;;
*)
echo var starts with something else
;;
esac
Looks alright, doesn’t it?
No, it’s does not. If that variable had not been assigned a value before or is of zero length, you will see an ugly syntax error occur.
Therefore enclose the variable in double quotes like here:
case “$var” in
x*)
echo var starts with x
;;
*)
echo var starts with something else
;;
esac
There is no good excuse for not doing it anywhere. It may look ugly and unnecessary, but it will help. That’s the way shell scripting is. I learned this from Jürgen Gulbins around 1987, when I enjoyed working for him. This series of articles is dedicated to him. I owe him a lot.