Is this a valid HTML? https://validator.w3.org/ seems to require this as minimal HTML to validate successfully.

    <!DOCTYPE html><html><title>0</title>

I would thus fix your 1 line shell static site generator like this.

    echo '<!DOCTYPE html><html><title>0</title>' > index.html

You can trim <html> tag and still get valid html: <!DOCTYPE html><title>0</title>

It's still a site even if it doesn't validate. HN (news.ycombinator.com) generates more than 100 errors on that validator. Doesn't mean HN isn't a site.

You can even go more minimalist. An empty file is a site too.

Still takes one line, but it would be smaller in size

    touch i

No need to use such a bloated tool as "touch" to create a site. Your shell can do it:

  > index.html

And there's ofcourse:

  <<eof > index.html
  <html>
  <p>hello, world! from
  $(whoami)</p>
  </html>
  eof

See also: m4.

    > index.html

You win.

Agreed. I concede!

    >index.htm

Two characters shorter and will work fine on most HTTP servers ;-)

Now you're just being pedantic, Peter!

Yes, but it looked like this was turning into a golfing thread ;-)

Snark aside, does it matter if most of the "site" is already in templates? Why shouldn't the templates be included in the metric?