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Thread: test if using dual monitors

  1. #1
    Join Date
    Jul 2012
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    Elmira, NY
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    197
    Distro
    Ubuntu 14.04 Trusty Tahr

    test if using dual monitors

    Is there a way to test if the computer is using dual monitors or not regardless of which graphics card is being used? I was looking for more of a terminal approach, one that would return false or true, or be able to parse the output for the same type of answer?
    Ubuntu 13.04, x86_64, 3.8.0-19-generic, gnome3 desktop, multi-boot
    Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz, 8GB RAM, dual monitors, AMD Radeon HD 6770
    Python 3.2.3 and 2.7.3, tkinter 8.5, pyqt 4.8.1, pygame 1.9.2 pre
    https://github.com/metulburr

  2. #2
    Join Date
    Jan 2008
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    Nappanee, IN
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    602
    Distro
    Xubuntu 12.04 Precise Pangolin

    Re: test if using dual monitors

    Look at the output of xrandr and scan for connected in the output.

  3. #3
    Join Date
    Jul 2012
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    Elmira, NY
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    197
    Distro
    Ubuntu 14.04 Trusty Tahr

    Re: test if using dual monitors

    This being my computer with two mintors
    Code:
    metulburr@ubuntu:~$ xrandr
    Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 3840 x 1920
    DFP1 disconnected (normal left inverted right x axis y axis)
    DFP2 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 886mm x 498mm
       1920x1080      60.0*+   59.9     30.0     24.0     30.0     24.0  
       1776x1000      59.9     24.0     30.0  
       1680x1050      60.0     59.9     24.0     24.0  
       1400x1050      60.0     59.9     24.0     24.0  
       1600x900       59.9     24.0  
       1360x1024      60.0     59.9     24.0     24.0  
       1280x1024      60.0     24.0  
       1440x900       59.9     24.0  
       1280x960       60.0     24.0  
       1360x768       60.0     24.0  
       1280x768       60.0     24.0  
       1280x720       60.0     59.9     24.0  
       1024x768       24.0     60.0  
       1152x648       59.9  
       800x600        24.0     60.3  
       720x480        24.0     30.0     60.0     30.0     59.9  
       640x480        24.0     60.0     59.9  
    DFP3 disconnected (normal left inverted right x axis y axis)
    DFP4 disconnected (normal left inverted right x axis y axis)
    CRT1 disconnected (normal left inverted right x axis y axis)
    CRT2 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 509mm x 286mm
       1920x1080      60.0*+
       1600x1200      60.0  
       1680x1050      60.0  
       1400x1050      60.0  
       1600x900       60.0  
       1360x1024      60.0  
       1280x1024      60.0  
       1440x900       59.9  
       1280x960       60.0  
       1280x768       60.0  
       1280x720       60.0  
       1024x768       60.0  
       800x600        60.3  
       640x480        59.9  
    metulburr@ubuntu:~$
    so CRT@ and DFP2 would be the two mintors?


    and this being another one of my comuters with just one monitor:
    Code:
    metulburr@Ubuntu:~$ xrandr
    Screen 0: minimum 8 x 8, current 1280 x 800, maximum 8192 x 8192
    VGA-0 disconnected (normal left inverted right x axis y axis)
    TV-0 disconnected (normal left inverted right x axis y axis)
    LVDS-0 connected 1280x800+0+0 (normal left inverted right x axis y axis) 331mm x 207mm
       1280x800       60.0*+
    HDMI-0 disconnected (normal left inverted right x axis y axis)
    metulburr@Ubuntu:~$
    So i am assuming that one connected means one moneitor, and two connected means two? Is that right?

    But then if i shut off my 2nd monitor, i get what i think is the same response:
    Code:
    metulburr@ubuntu:~$ xrandr
    Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 3840 x 1920
    DFP1 disconnected (normal left inverted right x axis y axis)
    DFP2 connected (normal left inverted right x axis y axis)
       1920x1080      60.0 +   59.9     30.0     24.0     30.0     24.0  
       1776x1000      59.9     24.0     30.0  
       1680x1050      60.0     59.9     24.0     24.0  
       1400x1050      60.0     59.9     24.0     24.0  
       1600x900       59.9     24.0  
       1360x1024      60.0     59.9     24.0     24.0  
       1280x1024      60.0     24.0  
       1440x900       59.9     24.0  
       1280x960       60.0     24.0  
       1360x768       60.0     24.0  
       1280x768       60.0     24.0  
       1280x720       60.0     59.9     24.0  
       1024x768       24.0     60.0  
       1152x648       59.9  
       800x600        24.0     60.3  
       720x480        24.0     30.0     60.0     30.0     59.9  
       640x480        24.0     60.0     59.9  
    DFP3 disconnected (normal left inverted right x axis y axis)
    DFP4 disconnected (normal left inverted right x axis y axis)
    CRT1 disconnected (normal left inverted right x axis y axis)
    CRT2 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 509mm x 286mm
       1920x1080      60.0*+
       1600x1200      60.0  
       1680x1050      60.0  
       1400x1050      60.0  
       1600x900       60.0  
       1360x1024      60.0  
       1280x1024      60.0  
       1440x900       59.9  
       1280x960       60.0  
       1280x768       60.0  
       1280x720       60.0  
       1024x768       60.0  
       800x600        60.3  
       640x480        59.9  
    metulburr@ubuntu:~$
    Last edited by micahpage; June 30th, 2013 at 12:25 AM.
    Ubuntu 13.04, x86_64, 3.8.0-19-generic, gnome3 desktop, multi-boot
    Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz, 8GB RAM, dual monitors, AMD Radeon HD 6770
    Python 3.2.3 and 2.7.3, tkinter 8.5, pyqt 4.8.1, pygame 1.9.2 pre
    https://github.com/metulburr

  4. #4
    Join Date
    Jan 2008
    Location
    Nappanee, IN
    Beans
    602
    Distro
    Xubuntu 12.04 Precise Pangolin

    Re: test if using dual monitors

    Your computer never knows when the monitor is on except when the computer is booting and attempting to read the EDID of the monitor , so, yes, when you turn off a monitor, the computer still thinks it is connected. If you are looking for something to check when a monitor is turned off, that is a different color of horse.

  5. #5
    Join Date
    Oct 2005
    Location
    Al Ain
    Beans
    8,271

    Re: test if using dual monitors

    Technically, there is nothing stopping you to talk to the screen serial port directly and see whether there is something out there. It may even be as simple as using echo to send a string to a device in /dev and cat or read to get the response, but I never tried it.

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