The command echo “users” | ssh myserv does not return anything.. Why?

Question

The command echo "hostname" | ssh myserv returns the hostname, but echo "users" | ssh myserv does not return anything?

When I ssh on the server then run the command users, it returns my user name (since I'm connected on it :-' ).

Answer 1

users only shows users who are logged into a terminal (as recorded in utmp). echo users | ssh myserv doesn't create a terminal (it's not an interactive session), so that session isn't listed. The more common ssh myserv users similarly executes the command without creating a terminal. On the other hand, ssh -t myserv users (where -t forces a terminal to be created) should show you.

Compare also ssh -t myserv 'tty; who' (shows you logged in on that tty) with ssh myserv 'tty; who' (not a tty).

Answer 2

Try it this way:

ssh myserv users

Answer 3

I get an error when I attempt this. Some programs require a tty. Also keep in mind that who, and users are a special case, they are looking specifically at login sessions.

# echo users | ssh host
stdin: is not a tty

See:

man sshd_config

UseLogin Specifies whether login(1) is used for interactive login sessions. The default is “no”. Note that login(1) is never used for remote command execution.

man users

users - print the user names of users currently logged in