As far as I can see from all the examples I can find the following is correct:

if [ "$x" = "valid" ]; then

So, if that's how an if has to work, and a command should be within "$(command)" why does the following work:

if pgrep process; then
echo "Yes"
else
echo "No"
fi

I know that returns a number, but you'd check for a number in the first example. I'm fine with it working, that doesn't bother me, I just want to understand why.

Many thanks.