How to check if a file is empty in Bash?

Question

I have a file called diff.txt. I Want to check whether it is empty.

I wrote a bash script something like below, but I couldn\'t get it work.

Answer 1

While the other answers are correct, using the "-s" option will also show the file is empty even if the file does not exist.
By adding this additional check "-f" to see if the file exists first, we ensure the result is correct.

if [ -f diff.txt ]
then
  if [ -s diff.txt ]
  then
    rm -f empty.txt
    touch full.txt
  else
    rm -f full.txt
    touch empty.txt
  fi
else
  echo "File diff.txt does not exist"
fi