RE: Is there a way to tell s_client to just "send a command" and quit?

Mark Christian wrote:

> On Thu, 2025-09-25 at 14:25 -0700, Dan Mahoney wrote:
> >
> > I'm writing some certificate checks that call s_client to fetch my
> > cert, but openssl s_client is blocking.  Is there an easy way to tell
> > it "hang up as soon as negotiation settles?"

> Perhaps there is a better way than piping echo to openssl. If not:

> % echo | openssl s_client -connect ...

Even the newline from echo is unnecessary, so you can save a few characters:

$ openssl s_client -connect ... </dev/null

(The </dev/null can go anywhere after the command name, actually, so "openssl </dev/null s_client ..." works too.)

On Windows, use "<nul" rather than "</dev/null".

In any case, the idea is to give s_client an EOF on stdin right off the bat.

--
Michael Wojcik
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