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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.

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You mention ssh, is it relevant? If so the display number is probably not your display. You will not normally specify a display number as the DISPLAY environment variable is used by default. – richard Mar 13 '11 at 22:50
up vote 5 down vote accepted

It's included by (obscure) reference.


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

And buried down a ways in X(7):


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.

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