the test -s for the “if” statement

Question

I have a question and i would be grateful for the answer if somebody knows one. Ok, to the point. In one of my scripts i have following expression, it is not clear for me form m

Answer 1

-s checks not only if the file exists, but also if it contains any data (that is, if it has a size greater than 0 bytes). This is more than the -a option (which is, in fact, a synonym of -e) does, which only tests if the file exists.

touch foo
[[ -a foo ]] && echo "File foo exists"
[[ -s foo ]] || echo "File foo exists, but is size 0 bytes"

(I have wondered what the rationale for -a is, since I'm not aware that it does anything different from -e.)