Only allow living breathing user to issue a command

Question

I have an application that accepts input from stdin, let's call this application suman-f which can be run via the command line. I'd like to limit the input to the real human user only and not allow input from automated programs. The reason for this is because if multiple processes are sending information to stdin, it will get garbled, as there is only one information channel but multiple communicators.

Is there a way to prevent anything but a human executing suman-f via a terminal?

Or if there is some magical way to multiplex stdin, I'd love to hear about it.

What do you mean by "multiple processes sending information to stdin"? — Michael Homer, Jul 11 '17 at 06:33
If you have 5 programs writing to the stdin of another program X, how does X piece together the messages? — Alexander Mills, Jul 11 '17 at 06:38
not sure why this question got a downvote...@MichaelHomer multiple processes could potentially write to suman-f stdin simultaneously...not sure how else to describe it — Alexander Mills, Jul 11 '17 at 06:59
"multiple processes are sending information to stdin" That is not normal. People will be better able to help you if you describe exactly how this is happening. — John1024, Jul 11 '17 at 07:11
it's not that normal, but it's not that hard to imagine either right? UDP messages arriving to a UDP server has the same kind of problem, it's not necessarily easy to multiplex (I believe). — Alexander Mills, Jul 11 '17 at 07:24
I'm afraid I don't understand well the logic behind your question. If multiple human users send information to stdin at the same time, it would get garbled too. — dr_, Jul 11 '17 at 07:27
I couldn't think of a better word than eponymous - "suman-f" is the program name and it is run by executing suman-f at the command line. — Alexander Mills, Jul 11 '17 at 07:41
yeah. it was a misuse of the word, I removed it from the question — Alexander Mills, Jul 11 '17 at 07:48
this seems like a pretty legit question with interesting ramifications, wish people would think outside the box, or appreciate a question outside of the box. — Alexander Mills, Jul 11 '17 at 07:49
Is this question about multiplexing or about preventing future simulated human brains from logging on? It's unclear what you're asking. — Alexander, Jul 11 '17 at 08:06

score 1 · Accepted Answer · edited Jun 11 '20 at 14:16

1

Short answer is no.

Unix system has no way to know if stdin of a particular process is handled by a human.

tty

your best approximation is tty. (see man tty).

tty (terminal) are the way to interact with system ( see What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'? ).

This is how it works

if tty -s
then
    echo a human might be reading "or not)"
else
    echo output is a file
fi

in other word

if tty -s return false, you know output is a file (not a user),
if tty -s return true, you don't know.

This allow different formating (like ls), or prevent from interactive usage.

edited Jun 11 '20 at 14:16

Community

1

answered Jul 11 '17 at 08:01

Archemar

31,554

yeah that's what I was thinking. an approximation is ok. – Alexander Mills Jul 11 '17 at 08:06
2

How would tty help? (Think ssh -t... as just one example.) – Chris Davies Jul 11 '17 at 08:39
1

that's why I say "approximation" – Archemar Jul 11 '17 at 09:19
this guy gets the question, why is it so hard for other people to understand the question. – Alexander Mills Aug 08 '17 at 06:12

Only allow living breathing user to issue a command

1 Answers1

tty