Re: howto serialize tasks in .xsession

[Gregory Seidman <gss+debian@cs.brown.edu>]

On Sat, Feb 28, 2004 at 03:50:17PM -0800, Nano Nano wrote:
} I run a hybrid desktop: gnome-control-center is installed, but not 
} metacity.  Fluxbox is my WM; but I remove gnome-session as a Session 
} Manager so I have No Session Manager.  Here is my .xsession:
} 
} #!/bin/sh
} ARGS="--hide-menubar --window-with-profile=Default"
} #gnome-control-center
} gnome-settings-daemon --oaf-activate-iid=OAFIID:GNOME_SettingsDaemon --oaf-ior-fd=21 &
} xscreensaver -nosplash &
} kdeinit &
  ( sleep 5
} gbuffy &
} #xmms &
} gnome-terminal $ARGS --geometry=80x25+1+22 &
} gnome-terminal $ARGS --geometry=95x25+582+22 &
} gnome-terminal $ARGS --geometry=80x40+1+418 &
} gnome-terminal $ARGS --geometry=95x40+582+418 &
  )
} exec fluxbox
[...]
} The problem is if gbuffy or gnome-terminal starts before 
} gnome-settings-daemon, themes and various gnome-ish things are broken.  
} It's a classic race conditions.
} 
} How can I serialize the tasks?  Remember, none can block.  
} gnome-settings-daemon doesn't return.

Note the two added lines above. This is the simplest way to deal with
that sort of thing. Adjust the length of the sleep to taste. A better
way is to use a spinlock wrapped around lsof or netstat right after the
gnome-settings-daemon call (note that calling it without any arguments
works at least as well):

#...
gnome-settings-daemon &
GSDPID=$!
while lsof -u$USER | awk 'BEGIN { found = 0; }
	($2 == "'$GSDPID'") && ($8 ~ /orbit-'$USER'/) { found = 1; next }
	END { exit found }'
do
	sleep 1
done
sleep 1
#...

This will run lsof once a second until gnome-settings-daemon has set up
its unix socket, then sleep one extra second for safety, then proceed.
Note that it uses the pid gnome-settings-daemon started with, so other
instances of the daemon will be ignored.

--Greg