Any difference between "send_user" and "puts" in Expect?

Question

It's not clear to me if send_user is the same as puts. Every time I want to send an informative message to the user, I would wonder which one I should use. From Expect's man page, it seems like send_user is the same as puts but then what is send_user used for?

Answer 1

Another difference I just discovered between the two, apart from the newline thing, is that if you're using log_file in your Expect script, statements sent via send_user will make it into the logfile, whereas statements sent with puts do not. If you're automating some Expect scripts which aren't being run on your actual console, that can make a big difference.

Answer 2

The main difference is that puts automatically appends a newline and send_user does not. In this regard, puts -nonewline is more analagous to send_user.

send_user also "inherits" some options from expect's send, such as -s and -h (check the expect man page for details). See http://99-bottles-of-beer.net/language-expect-249.html for a usage of the -h flag.

I cannot speak to how they're implemented at the C-level.