in variable assignment. When you write bash shell scripts, you want to avoid these innocent-looking mistakes. We all fall into these traps at some point, especially when we first write bash scripts.
You define a bash variable, say $somevar. Later, you need to test if it is equal to some string, say "linux".
5 if [ $somevar == "linux"]
6 then ...
25 exit 0
Depending on the value of $somevar at the time of the test, you can see some puzzling errors:
- If $somevar is null (""), then you will see this error:
./myscript.sh: line 5: [: =: unary operator expected
- If $somevar has embedded spaces, e.g., "tux is great", you will see this error:
./myscript.sh: line 5: [: too many arguments
Now, you know this trap, don't fall into it.
A good defence is to always enclose the bash variable in quotes:
if [ "$somevar" == "linux"]