Always use bc for floating point math of any kind in any shell
script. Here’s a great example of how Zsh fucks you while trying to
help you out. First, the script as you should write it using bc:
foo=2
bar=3.3
tot=0
tot=$(echo "scale=2; $foo + $bar" | bc)
echo $tot
This does exactly what you want with absolute control over the precision.
$ sh /tmp/foo
5.3
In POSIX shell you could try to use floating point math and be reminded that you just cannot. POSIX shell knows its limitations and openly manages your expectation properly. This is nice and safe. You can’t even write it and have it run at all.
foo=2
bar=3.3
tot=0
tot=$((foo+bar))
echo $tot
This fails.
$ sh /tmp/foo
/tmp/foo: 6: Illegal number: 3.3
What about bash?
/tmp/foo: line 6: foo + 3.3: syntax error: invalid arithmetic operator (error token is ".3")
It also fails and tells you why, like a good friend, your second love after POSIX.
But then Zsh fucking lies to you. It pretends to know what you want and turns out to fuck you over like your ex-wife.
$ zsh /tmp/foo
5.2999999999999998
If it had just failed like sh you would be better off, but instead it
happily accepted your shitty code that its floating point processor
can’t handle you and now billions of people have died or gotten
instantly rich because of your dumb-ass use of Zsh instead of the
standard. But oh my God, Oh-My-Zsh is so fucking cool! 🤦