Capturing Screenshot of terminal application via shell script?

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

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

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