Xmessage over ssh

command lineoptionsx11

The following command prints a message over ssh :
xmessage Message -display :0 &
How does it work? there is no -display option in xmessage's man page.

Best Answer

It's included by (obscure) reference.

SEE ALSO

X(7), echo(1), cat(1)

And buried down a ways in X(7):

OPTIONS

Most X programs attempt to use the same names for command line options and arguments. All applications written with the X Toolkit Intrinsics automatically accept the following options:

-display display

This option specifies the name of the X server to use.

followed by a number of other X Toolkit Intrinsics (Xt) standard options. More modern toolkits have similar common options, which you can see with the --help-all option.

Related Solutions

Ssh – How does SSH display the message “The authenticity of host .. can’t be established”

ssh opens the controlling terminal directly via /dev/tty and that's where it's writing that message.

It's the same fd ssh is using to interact with the user, to read passwords, etc. This allows the user to redirect the stderr or stdin of ssh transparently.

$ strace -f -o /tmp/strace ssh -o UserKnownHostsFile=/dev/null localhost
The authenticity of host 'localhost (::1)' can't be established.
ECDSA key fingerprint is SHA256:XXXXXXXXXXXXX8XXXXXX8XXXX4XXXXXXXXXXXX3XXXX.
Are you sure you want to continue connecting (yes/no)? ^C
$ egrep 'open|write' /tmp/strace
...
3609  openat(AT_FDCWD, "/dev/tty", O_RDWR) = 4
3609  write(4, "The authenticity of host 'localh"..., 197) = 197

Shell – What does the option -9 mean for killall

(I assume you're talking about the Linux killall command.)

The option -9 is listed in a generic way under -SIGNAL. The description specified that

Signals can be specified either by name (e.g. -HUP or -SIGHUP) or by number (e.g. -1) or by option -s.

So you can use killall -9 or killall -s 9 to send signal number 9, killall -42 or killall -s 42 to send signal number 42, etc. You can use killall -KILL or killall -s KILL to send the KILL signal, etc.

On traditional and modern Unix systems and on most POSIX systems, signal number 9 is the kill signal. On many systems you can use kill -l 9 to list the signal name corresponding to number 9; in bash, kill -l lists the recognized signal names with their corresponding numbers.

Best Answer

Related Solutions

Ssh – How does SSH display the message “The authenticity of host .. can’t be established”

Shell – What does the option -9 mean for killall

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