Hack and / - Lightning Hacks
One of the more interesting parts of any conference is the lightning talks. If you haven't experienced one, a lightning talk typically features a number of different speakers, each giving a short (5–20 minutes) presentation. Lightning talks take advantage of the fact that often a speaker has an interesting topic to present, but the topic won't fill an entire hour time slot. So, lightning talks round up each of these speakers one after the other in the same time slot. Because of the variety of information and the fast nature of lightning talks, they can be really informative, interesting and definitely fun.
As I was considering what topic to cover for this month's column, I realized I had a number of different hacks I'd like to mention, but none that could really fill a full column. In the spirit of lightning talks, I decided to put all of these hacks together in true rapid-fire fashion.
In the March 2008 issue of Linux Journal, I introduced the wmctrl tool and discussed how to use it to move, resize, shade and do all sorts of window management tasks from the command line. I also introduced a few scripts I had written and bound to keys to resize and shade a few different windows on my desktop. Near the end of that article, I mentioned:
My next project is to create a “reset” script that moves all the windows on all of my desktops to precise locations and sizes, in case they all get moved around and resized. Sure, I could do all this by hand, but then I'd miss this great opportunity for automation.
Well, shortly after I wrote that, I completed my reset script. This script goes from desktop to desktop (or because I use Compiz, viewport to viewport) and moves and resizes windows per my specifications. I've added comments to explain particular sections:
#!/bin/sh # First save my current viewport so I can return # to it after I'm done SAVED_VP=`wmctrl -d | perl -ne '/VP: (\d+,\d+)/; print $1;'` # Then, move to the first viewport (at 0,0). Because it # can take a second or two for this to take effect, # I've opted to create a while loop that will # continue to attempt to switch to that viewport # until it detects it is actually there. VP=0,0 while [ `wmctrl -d | perl -ne '/VP: (\d+,\d+)/; ↪print $1;'` != $VP ]; do wmctrl -o $VP done # Now resize, move, and change state of particular # windows (see the wmctrl man page, or my wmctrl # column for more information on the options). wmctrl -r 'Eterm Main 1' -e '0,0,0,645,420' wmctrl -r 'Irssi Term' -e '0,469,0,810,500' wmctrl -r 'Irssi Term' -b add,shaded wmctrl -r 'Irssi Term' -b add,below wmctrl -r 'gkrellm' -b add,sticky wmctrl -r "Irssi Notify Term" -e '0,1180,550,100,230' # I now switch to the second viewport. As my screen # is 1280x768, the second viewport is at 1280,0. # If I wasn't sure, I could switch to that viewport # and check the output of wmctrl -d for the proper coordinates. VP=1280,0 while [ `wmctrl -d | perl -ne '/VP: (\d+,\d+)/; ↪print $1;'` != $VP ]; do wmctrl -o $VP done wmctrl -r "Mozilla Firefox" -e '0,5,0,1040,708' # Finally I switch back to my original viewport # so I'm back where I started. wmctrl -o $SAVED_VP
Although there are certainly a lot of commands in that script, it actually didn't take long to write. Most of the script is simply one wmctrl command after another, and I spent a majority of the time actually fine-tuning the locations of each window and figuring out the best way to switch viewports. If your desktop environment uses multiple desktops instead of one desktop with multiple viewports, you would use the -s option to change desktops instead of the -o option, which is used for viewports. You also would need to change the logic in the while loop to something more like:
DESKTOP=1 while [ `wmctrl -d | perl -ne '/^(\d+).*?\*/; ↪print $1;'` != $DESKTOP ]; do wmctrl -s $DESKTOP done
Although I normally use my laptop with its own built-in screen, I frequently give presentations, so I need to display on both the LCD and the external VGA connector. Unfortunately, my laptop's function keys to toggle between those states don't currently work in Linux, so I've had to put it into a script paired with a keybinding.
The xrandr program works great with my laptop to toggle between displays, so my script first examines the output of xrandr to see whether the VGA port is connected, and if so, it adds it as a display. Otherwise, it disables VGA. I also added a line to echo some text to osd_cat. I installed this program so that I would get some output on the screen to let me know which mode my script had chosen. When I'm ready to output to a projector, I just connect it to my laptop and run the script. When I'm finished with the presentation, I disconnect it and run the script again:
#!/bin/sh if xrandr | grep -q 'VGA connected'; then echo "LVDS + VGA" | osd_cat --shadow=2 --align=center ↪--pos=bottom --color=green --delay=2 ↪--font=lucidasanstypewriter-bold-24 --offset 40 & # choose my laptop screen's resolution by default, # if that fails try the auto-detected mode xrandr --output VGA --mode 1280x768@60 || xrandr ↪--output VGA --auto else echo "LVDS only" | osd_cat --shadow=2 --align=center ↪--pos=bottom --color=green --delay=2 ↪--font=lucidasanstypewriter-bold-24 --offset 40 & xrandr --output VGA --off & fi
I also created a separate version of the script that spans across both screens instead of mirroring. I chose to span below my current screen (with the --below LVDS option), but most people probably will prefer to use --right-of or --left-of:
#!/bin/sh if xrandr | grep -q 'VGA connected'; then echo "LVDS + VGA span" | osd_cat --shadow=2 --align=center ↪--pos=bottom --color=green --delay=2 ↪--font=lucidasanstypewriter-bold-24 --offset 40 & xrandr --output VGA --mode 1280x768@60 --below LVDS || xrandr ↪--output VGA --below LVDS --auto else echo "LVDS only" | osd_cat --shadow=2 --align=center ↪--pos=bottom --color=green --delay=2 ↪--font=lucidasanstypewriter-bold-24 --offset 40 & xrandr --output VGA --off & fi
Kyle Rankin is a VP of engineering operations at Final, Inc., the author of a number of books including DevOps Troubleshooting and The Official Ubuntu Server Book, and is a columnist for Linux Journal. Follow him @kylerankin.
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- 2005 Linux Journal Readers' Choice Awards
- Kbuild: the Linux Kernel Build System
- Linux Mint 18
- Sony Settles in Linux Battle
- Introduction to Named Pipes
- Experimenting with New Methods in Voice over IP
- Advanced Packet Data Testing with Linux
- Overcoming Asymmetric Routing on Multi-Homed Servers
- Supercat Text Colorizer
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide