weblogs : azul : x-environment-variables

I often switch X servers while I'm running multiple shells and GNU screen sessions. This means that X clients that I run usually end up contacting the wrong X server and I have to spend a lot of time adjusting environment variables or restarting shells.

For example, I'm currently running 11 GNU screen sessions in my workstation, each with an average of 2 or 3 shells. If I go home and SSH into my workstation, many commands will continue to contact my workstation's X server (instead of using the SSH X forwarding tunnel or, often preferable, not contacting any X servers at all).

I decided to fix this.

First, I wrote an xload shell script that initializes X environment variables and runs a command:

#!/bin/sh
function load_env {
  if test -f ~/.afc-persistent-environment/$1
  then
    export $1=$(cat ~/.afc-persistent-environment/$1)
  else
    unset $1
  fi
}
load_env DISPLAY
load_env XAUTHORITY
exec "$@"

Then I added the following to my ~/.bashrc:

if ! test -d ~/.afc-persistent-environment
  mkdir ~/.afc-persistent-environment
fi

function save_env {
  if test "${!1}" == ""
  then
    rm ~/.afc-persistent-environment/$1
  else
    echo ${!1} >~/.afc-persistent-environment/$1
  fi
}

function xsave {
  save_env DISPLAY
  save_env XAUTHORITY
}

function xwrap {
  echo $* >> ~/.afc-xwrap
} 

function load_xwraps {
  for program in $(cat ~/.afc-xwrap)
  do
    alias $program="xload $program"
  done
}

load_xwraps

With this in place, I simply:

• Run xsave when I change X server (or when I decide not to use one) from a shell to make its X configuration global for all other shells (for X clients that I launch from them)
• Run xwrap passing X clients that I'd like to wrap with xload, so that the next time I launch them, they'll use the globally-saved configuration. For instance: xwrap xterm g4 vi vim ssh xlock gaim. Note that I only need to do this once per X client (ever).
• For launching X clients from programs other than the shell (which won't see the shell's aliases), substitute “program ...” with “xload program ...”.
• Run load_xwraps to reload the list of wraps. This is only needed after I run xwrap, which happens very rarely.

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