Multiple users of X monitors

J. Wood jwo at
Mon Jan 18 03:31:20 EST 1993

Has anyone any experience of using GRASS in a truly multi-user
environment ?

I am about to start teaching with GRASS which has been installed
on our central SGI Irix system. My problem is getting multiple
users to open the same graphics output (eg x0). Because GRASS is
installed on a single machine, as soon as a second person tries to
open x0, a lock file error results. 

This error does not occur on our network of SUNs because whenever
a graphics monitor is started a lock file is created in a subdirectory
that is named as the LOCAL machine name. When using X terminals (actually
PCs with Vista eXceed) they all have the same machine name lockfile

I thought perhaps one solution would be to create lots of new graphics
devices which instead of being called x0, x1 etc. would be called x_username.
Apart from being rather non-standard, and clumsy this also causes with the
latest versions of the X-driver which does not like more than graphics
window to be open simultaneously (colours become corrupted).

Another potential solution might be to modify the the file io.c in
$SRC/libes/raster to that the line

	hostname = G__machine_name();

	also appends G_who_am_i() to the machine name. This would give
a unique `machine name' to the lockfile of each user. 

Does anyone out there have any thoughts/solutions ?


Jo Wood
Academic Support for Spatial Information SysTems (ASSIST)
University of Leicester
Leicester LE1 7RH

E-mail: jwo at

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