UNIX is an operating system, not a commandline. You seem to be talking about the standard UNIX shell, sh or one of it's clones like bash, but could have as easily been using something like korn... or even been programming in C.... = and == are pretty common.
I've never seen code like your first example, probably because it doesn't work. ( ) brackets aren't statement grouping, they define arrays!
Code:
arr=(a = c)
echo ${arr[0]}
echo ${arr[1]}
echo ${arr[2]}
will print a, then =, then c. The = isn't even treated as an operator inside the ().
Inside the [[ ]] brackets, == is a pattern matching operator for strings, and = is a straight equality comparison. Outside of there, = is an assignment operator like
variable="something" and I don't think == does anything.
Also, your if statements aren't quite right. Try this:
Code:
if [[ $this = "that" ]]
then
echo "Something"
else
echo "Something else"
fi
