Capturing Screenshot of terminal application via shell script?

Question

Problem

Run iftop for 5 seconds, capture the screenshot and save it to a file.

iftop is a beautiful program for visualizing network traffic, but it doesn't have a batch mode where I can run it for few seconds and capture the output to a file.

So my idea is

• use commands like screen to create a virtual display and run iftop in it.
• look for any tools (screendump) to take a screen shot of the screen.

Any idea on how do I go with this?

Answer 1

I don't think you'll be able to do this with screen unless the output is actually rendered in a window, which probably defeats the point of using screen. However, the window does not have to be in the foreground.

The ImageMagick suite contains a utility called import you can use for this. If import --help gives you "command not found", install the imagemagick package, it will be available in any linux distro.

import needs the name of the window. iftop is a terminal interface, so to make sure you use the right name, you'll have to set the title of the GUI terminal it runs in. How you do that depends on which GUI terminal you use. For example, I prefer the XFCE Terminal, which would be:

Terminal -T Iftop -e iftop

Opens a new terminal running iftop with the title "Iftop". A screenshot of that can be taken:

import -window Iftop ss.jpg

If you are going to do this every five seconds, you probably want to instead open the window running a script so you can reuse the same terminal:

count=0;
while ((1)); do
    iftop &
    pid=$!
    sleep 1  # make sure iftop is up
    count=$(($count+1))
    import -window Iftop iftop_sshot$count.jpg
    kill $pid
    sleep 5
done

If the script is "iftopSShot.sh" then you'd start this Terminal -T Iftop -e iftopSShot.sh -- except you're probably not using Terminal. Most of the linux GUI terminals are associated with specific DE's, although they are stand-alone applications which can be used independently. I believe the name of the default terminal on KDE is Konsole and it follows the -T and -e conventions; for GNOME it is probably gnome-terminal (this may have changed) and it appears to use -t and not -T.

Beware import by default rings the bell, which will get irritating, but there is a -silent option.

Answer 2

screen can log to a file :

-L tells screen to turn on automatic output logging for the windows.

or make a copy of the current screen to a file :

hardcopy [-h] [file]

   Writes out the currently displayed image to the file file, or,
   if no filename is specified, to hardcopy.n in the  default directory,
   where  n  is the number of the current window.  This either appends
   or overwrites the file if it exists. See below.  If the option -h
   is specified, dump also the contents of the scrollback buffer.

If you have one screen session running, you can save it's current content with this command:

screen -X hardcopy

For saving to 100 separate files, 1 every 10 seconds:

for c in {1..100}; do screen -X hardcopy /my/dir/screen-$c; sleep 10; done

Answer 3

In a X environment:

---

Set dynamically the terminal title:

From our script, a way to change the terminal title using ansi sequences:

echo -e "\033]0;Term | myApp\007";

Capture a png by window title:

Now we can search for the window id by the exact title using wmctrl and pass the id to the import utility:

import -window $(wmctrl -l | grep -i 'Term | myApp' | awk '{print $1}') ~/Pictures/capture.png

---

Build a gif:

Example to tweak, take 5 captures every second then convert them in order to a gif using convert, in an infinite 2 seconds loop.

rm -f /tmp/*png && for i in {1..5}; do import -window $(wmctrl -l | grep -i 'Term | myApp' | awk '{print $1}') /tmp/$i.png && sleep 1; done && convert -delay 200 -loop 0 /tmp/*.png animation.gif

Answer 4

Couple of ideas:

1. You could use this script from this articled titled: Screenshot tool for repetitive screenshotting.

   #!/bin/bash
   # Screenshot tool for TIMS.
   #
   # -------------------------
   #
   # By regj 2012.05
   #
   # -------------------------
   #
   # Check for config file create if needed with sane defaults then exit.
   if [ ! -f $HOME/.scrotter ]; then
       echo "Creating scrotter config file ${HOME}/.scrotter"
       echo "scrotfldrbase=${HOME}/Desktop/scrots" > $HOME/.scrotter
       echo "fontsize=14" >> $HOME/.scrotter 
       echo "fillcolor=white" >> $HOME/.scrotter 
       echo "whiteterm=yes" >> $HOME/.scrotter
       echo "subw=130" >> $HOME/.scrotter
       echo "subh=5" >> $HOME/.scrotter
       echo "fontpath=/usr/share/fonts/dejavu/DejaVuSansMono.ttf" >> $HOME/.scrotter
       if [ $? = 0 ] ; then
           echo -e "Config file succesfully created. Adjust values if needed in ~/.scrotter.\nIf you use a black term background set whiteterm to no."
           echo "Current values:"
           cat $HOME/.scrotter
           echo "Rerun scrotter with --server-id if initial run"
           exit 0
       else
           echo "Something went wrong"
           exit 1
       fi
   fi
   
   # Source config file
   source $HOME/.scrotter
   
   # convert functions for white or black terminal
   conv_black () {
   convert -pointsize $fontsize \
       -font $fontpath \
       -fill $fillcolor \
       -draw "text ${xyplace} \"$(date "+%Y.%m.%d %H:%M"|sed -e ' s/\"/\\\"/g' )\"" \
       $scrotfldr/$srvid-$count.png $scrotfldr/$srvid-$count.png 
   }
   
   conv_white () {
   convert -pointsize $fontsize \
           -font $fontpath \
           -fill $fillcolor \
       -stroke black \
       -strokewidth 1 \
           -draw "text ${xyplace} \"$(date "+%Y.%m.%d %H:%M"|sed -e ' s/\"/\\\"/g' )\"" \
           $scrotfldr/$srvid-$count.png $scrotfldr/$srvid-$count.png
   }
   
   
   # Options
   case $1 in
   
   --server-id) echo "Setting srvid" ; echo $2 > /tmp/${USER}-scrot-srvid ; exit 0;;
   --reset-count) echo "0" > /tmp/$USER-scrot-count ; exit 0;;
   --clean-up) rm -f $scrotfldr/*.png ; rm -f /tmp/${USER}-scrot-* ; exit 0 ;;
   --help) echo "Options are:
           --server-id: Set servername used in test.
           --reset-count: Reset counter for enumerating png's.
           --clean-up: Delete png's in current serverfolder and reset counters and serverid.
           --help: This info." 
           exit 0;;
   
   # Uncomment below if you want to remove everything in your scrot folder with this script
   #--clean-all) if [ -z $scrotfldrbase ]; then 
   #       echo "Exiting .." ; exit 1
   #        fi 
   #       echo "NB: $scrotfldrbase will be removed recursively!"  
   #       rm -rI $scrotfldrbase/*  
   #       rm -f /tmp/${USER}-scrot-*
   #       exit 0 ;;
   
   esac
   
   # Check if serverid is defined, use if yes
   if [ -s /tmp/${USER}-scrot-srvid ]; then
       srvid=$(cat /tmp/${USER}-scrot-srvid)
       scrotfldr=$HOME/Desktop/scrots/$srvid
   else
       echo "Please set server id with --server-id option. # scrotter --server-id <servername>"
       exit 1
   fi
   
   # Check if root, exit if yes.
   if [ $(id -u) = 0 ]; then
       echo "Do not run as root!"
       exit 1
   fi
   
   # Create count file
   if [ ! -f /tmp/${USER}-scrot-count ]; then
       echo "0" > /tmp/$USER-scrot-count
   fi
   
   # Create Screenshot folder if not present
   if [ ! -d $scrotfldr ];  then
       mkdir -p $scrotfldr
   fi
   
   # Get active window ID
   activewin=$(xprop -root | grep "_NET_ACTIVE_WINDOW(WINDOW)" | grep "window id" )
   activewinid=${activewin:40}
   
   # Get geometry of window
   geowinw=$(xwininfo -id ${activewinid} | awk '/Width/ {print $2}')
   geowinh=$(xwininfo -id ${activewinid} | awk '/Height/ {print $2}')
   
   # Define X,Y placment of date text
   xyplace="$(($geowinw - $subw)),$(($geowinh - $subh))"
   
   # Get current count
   count=$(cat /tmp/${USER}-scrot-count)
   
   # Take screenshot
   import -window "$activewinid" $scrotfldr/$srvid-$count.png
   
   # Insert date stamp into screenshot use xyplace variable to adjust placement
   if [ $whiteterm = yes ] ; then
       conv_white
   else
       conv_black
   fi
   
   # Increment counter
   echo $(($count+1)) > /tmp/$USER-scrot-count
   

   Put the above in a file called scrotter and make it executable. When you run it the first time:

   $ ./scotter
   Creating scrotter config file /home/saml/.scrotter
   Config file succesfully created. Adjust values if needed in ~/.scrotter.
   If you use a black term background set whiteterm to no.
   Current values:
   scrotfldrbase=/home/saml/Desktop/scrots
   fontsize=14
   fillcolor=white
   whiteterm=yes
   subw=130
   subh=5
   fontpath=/usr/share/fonts/dejavu/DejaVuSansMono.ttf
   Rerun scrotter with --server-id if initial run
   

   Running it a 2nd time you'll get the usage:

   $ ./scrotter 
   Please set server id with --server-id option. # scrotter --server-id <servername>
   

   Now run it with a --server-id blah, and start taking screenshots:

   $ ./scrotter --server-id blah
   $ ./scrotter
   

   It will take screenshots of the active window. This would be modified into a looping structure or modified directly!

2. You could use the import command to take a screenshot and wrap that in whatever type of loop you like (for, whilte, etc.) depending on your needs. This aritcle, Timelapse Screenshots, has everything you need, I don't think you want to make the script run from a cron but everything else seems applicable.

   For example:

   # takes screenshot
   $ import -window root -display :0 -crop 958x490+20+128 "savedfiles/screenshot_$(date +%d%m%y-%H.%M).png"
   
   # makes a video out of a bunch of them
   $ mencoder "mf://screamshots/*.png" -mf fps=10 -o test.avi -ovc lavc -lavcopts vcodec=msmpeg4v2:vbitrate=800