How to trim whitespace from a Bash variable?

I have a shell script with this code:

var=`hg st -R "$path"`
if [ -n "$var" ]; then
    echo $var
fi

But the conditional code always executes, because hg st always prints at least one newline character.

• Is there a simple way to strip whitespace from $var (like trim() in PHP)?

or

• Is there a standard way of dealing with this issue?

I could use sed or AWK, but I’d like to think there is a more elegant solution to this problem.