Skip to main content

Zenity Progress Dialogue

Zenity is a nice and simple way to prettify Bash scripts, similar to kdialog, xdialog and a few others, but on the whole I think the best of the lot.  Though there is nothing preventing you from mixing them up if one has a feature that would be more useful for something.

I started using Zenity years ago, when there wasn't much documentation and consequently didn't use the progress dialogue the right way.  The result being that some scripts eventually broke.  For example, there was no information on how to make the progress bar progress - so I only used the whirr-whirr pulsate effect.

No Progress

In the past, I simply started a pulsater, pushed it into the background, saved the PID and later killed it when necessary, like this:

zenity --progress &
PID=$!
echo "Do something"
kill $PID

That used to worked fine, but recently on Fedora 22, it just sits there and does nothing.  It won't even blink.  Dead as a doornail.  Bah, humbug...

When All Else Fails...

Eventually, I found the documentation and RTFMed:
https://help.gnome.org/users/zenity/stable/progress.html.en

The problem is that the progress dialog has a new bug and it expects to receive something over stdin in order to get going.  If it never gets anything, it does nothing - in previous versions it worked fine in the background, but no-more.  When it is pushed into the background with &, it just sits there and sulks.

The correct way to make a progress pulsater that must do something and exit based on a condition, at which point one has to stop the pulsater, is like this:
 
CNT=0
(
while TRUE, do
  echo "This Will Do Nothing"
  echo "#Change The Text"
  sleep 5
  let "CNT+=1"

  if [ "$CNT" -eq 10 ]; then
    # Close the progress dialog with 100%
    echo "100"
    exit 0
  fi

  echo "Continue doing nothing"
done
) | zenity --progress \
--width=350 \
--title="The Title"
--text="The Default Text" \
--no-cancel \
--auto-close \
--pulsate

The --auto-close parameter will cause the progress dialogue to stop when you echo "100" percent.

An echo statement that starts with a # will change the text and one without, will be ignored.  The --no-cancel will suppress the Cancel button, since it doesn't make sense.

La voila!

Comments

Popular posts from this blog

Unlock CRA PDF Forms

Unlock Canada Revenue Agency PDF Forms It appears that there is a relatively new PDF feature to prevent casual copying and saving of a file and that some programs save PDF files with these foolish features active by default.  Many forms from the Canada Revenue Agency are locked in this way, which makes it difficult to do one's taxes, since one can fill the form, but cannot save it.  One can only print the form.  It should be possible to print to a file or export it to a new PDF file, but it is far better to reset the annoying anti-taxpayer flags, since the 'printed' form cannot be edited easily any more and I always manage to make a mistake or three that need to be corrected after review. If there is a Linux (virtual) machine handy, install qpdf and use it to reset the silly flags: $ su - password # dnf update # dnf install qpdf # exit $ qpdf --decrypt lockedfile.pdf unlockedfile.pdf One doesn't need a password to unlock these flags, so the fix is instant. La voila! He...

Parasitic Quadrifilar Helical Antenna

This article was reprinted in OSCAR News, March 2018:  http://www.amsat-uk.org If you want to receive Satellite Weather Pictures , then you need a decent antenna, otherwise you will receive more noise than picture. For polar orbit satellites, one needs an antenna with a mushroom shaped radiation pattern .  It needs to have strong gain towards the horizon where the satellites are distant, less gain upwards where they are close and as little as possible downwards, which would be wasted and a source of noise.  Most satellites are spin stabilized and therefore the antenna also needs circular polarization, otherwise the received signal will flutter as the antennas rotate through nulls. The helical antenna, first proposed by Kraus in 1948, is the natural solution to circular polarized satellite communications.  It is a simple twisted wire - there seems to be nothing to it.  Various papers have been published on helix antennas, so the operation is pretty well ...

Weather Satellite Turnstile Antennas for the 2 meter Band

NEC2, 2 m band, 146 MHz, Yagi Turnstile Simulation and Build This article describes a Turnstile Antenna for the 2 meter band, 146 MHz amateur satcom, 137 MHz NOAA and Russian Meteor weather satellites.  Weather satellite reception is described here .  A quadrifilar helical antenna is described here .   Engineering, is the art of making what you need,  from what you can get. Radiation Pattern of the Three Element Yagi-Uda Antenna Once one combine and cross two Yagis, the pattern becomes distinctly twisted. The right hand polarization actually becomes visible in the radiation pattern plot, which I found really cool. Radiation Pattern of Six Element Turnstile Antenna Only a true RF Geek can appreciate the twisted invisible inner beauty of a herring bone antenna... Six Element Turnstile Antenna Essentially, it is three crosses on a stick.  The driven elements are broken in the middle at the drive points.  The other el...