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Suppose I did an export DISPLAY=:1 in an X forwarded ssh session. Now I want to reset it back to its original value so that when I launch X apps they show up on my screen and not on :1. Is there any way to find what it was and set it to that ? Or does the value get lost irrevocably once it is overwritten ?

I don't want to have to restart ssh session just because I changed the value of DISPLAY.

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1 Answer 1

up vote 3 down vote accepted

You can save it into another variable first:

export DISPLAY_BACKUP=$DISPLAY
export DISPLAY=:1

To restore it back, do:

export DISPLAY=$DISPLAY_BACKUP

In case the DISPLAY variable was not saved, you can use the following code snippet (found here) to try to get its original value:

netstat -lnt | awk '
sub(/.*:/,"",$4) && $4 >= 6000 && $4 < 6100 {
    print ($1 == "tcp6" ? "ip6-localhost" : "localhost:") ($4 - 6000)
}'

Remote displays correspond to open TCP ports above 6000; accessing display number N on machine M is done by connecting to TCP port 6000+N on machine M.

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Actually, I am asking for the case where I did not save it. Is it possible to restore the display then ? I mean there must be some way to find out what the real display value is ! –  AnkurVj May 24 '12 at 13:56
    
@AnkurVj I would say it is not possible to do that (unless you can guess the old value). Of course you can always restart the SSH connection. –  betabandido May 24 '12 at 14:05
    
@AnkurVj Probably the display value was something like localhost:10.0. But that will depend on whether other X11 sessions are active. –  betabandido May 24 '12 at 14:09
    
okay, that seems more effort than restarting ssh session. Although seems a legit hack to find out what I am looking for. Thanks ! –  AnkurVj May 24 '12 at 14:17

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