== A silly trick with X

Once upon a time, I was at home and really needed to see something
that was displayed on my screen at work. This being Unix, there was no
convenient remote desktop add-on that would have let me mirror my work
display to home, but this being Unix, there are ways around that.

(Also, I was connecting over a [[slow dialup PPP connection
../linux/DSLNeed]], so a live remote desktop thing would have
been difficult anyways.)

My first attempt was simple; ssh in to the work machine and do
_DISPLAY=:0 xwd -out /tmp/screen.xwd_. This generated a large image
that was unfortunately full of a lot of black, because I was [[running
a screen locker ../sysadmin/ScreenlockHabit]], and the X screen locker
actually puts a real window up on top of everything on the screen,
instead of having a special side channel into X.

No problem; this is Unix and I had a hammer:

* ssh in to work
* _export DISPLAY=:0_
* kill the xlock process
* _xwd_ the now revealed screen, complete with the window I needed
  to read
* run _nohup xlock >/dev/null 2>&1 </dev/null &_ to re-lock my screen

(After all, xlock doesn't care exactly where it's being started from;
all it needs is a _$DISPLAY_ and enough privileges on the display.)

Technically I believe I didn't use _xwd_, but I've now forgotten
whatever screen dump program it was. These days I would use _import_
from ImageMagick; however much ImageMagick makes me wince vaguely with
its swiss army chainsaw approach to life, it's convenient.