Take screenshots in background silently for archive purposes

I have just started learning Ubuntu.
I don't know this method is proper or not.
I Could achieve it in the below way.

I have created a script like this named ScreenShot.sh in the folder /usr/local/bin

#!/bin/bash

# NAME: ScreenShot.sh
# PATH: /usr/local/bin
# DESC: Take Screenshots at every specified intervals with "watch -n 10 ScreenShot.sh" Command
# DATE: Oct 12th 2018

sudo gnome-screenshot -d 0

sudo chmod a+x /usr/local/bin/ScreenShot.sh

when i start the system and wanted to start the screen capture at every 10secs,

i run this command

sudo watch -n 10 ScreenShot.sh

i have configured my default folder, image type to be saved, with dconf editor in gnome-screenshot section.

Sounds are stopped by dconf settings under sound section

I do the same thing. This is the script that I wrote, called screenlog-capture:

#! /bin/bash
window_name() {
  xwininfo -id "$1" | \
    grep "^xwininfo: Window id" | \
    LC_CTYPE=C LC_COLLATE=C sed  's/^[^"]*"\(.*\)"$/\1/' | \
    sanitize-filename
}

window_class() {
  xprop -id "$1" | grep "^WM_CLASS(STRING)" | cut -d '"' -f 4
  # Or we could use _NET_WM_PID(CARDINAL) -> process name
}

if [ ! -d "$RAMTMP" ]
then
  echo "RAMTMP needs to be set."
  exit 1
fi
if [ ! -e /usr/bin/puzzle-diff ]
then
    echo 'Error: puzzle-diff not installed!'
    exit 1
fi

rootdir="$HOME/screenlog"
if [ ! -w "$rootdir" ]
then
  echo 'Error: screenlog dir not writable'
  exit 1
fi
if [[ $(qdbus org.cinnamon.ScreenSaver /org/cinnamon/ScreenSaver org.cinnamon.ScreenSaver.GetActive) == true ]]
then
  exit
fi
du=$(df -Plh "$rootdir" | sed -n -e '2s/.* \([0-9]\+\)% .*/\1/' -e '2p')
if [ "$du" -ge 98 ]
then
  exit
fi
win_id=$(xprop -root | grep "^_NET_ACTIVE_WINDOW(WINDOW)" | cut -d ' ' -f 5)
win_name=$(window_name "$win_id")
parent_id=$(xprop -id "$win_id" | grep "^WM_TRANSIENT_FOR(WINDOW)" | cut -d ' ' -f 5)
if [ "$parent_id" ]
then
  win_class=$(window_class "$parent_id")
else
  win_class=$(window_class "$win_id")
fi
case "$win_class" in
  # Firefox-bin is full-screen YouTube video (for example)
  Gq|Geeqie|GQview|Firefox-bin|Plugin-container|Gimp|mplayer2)
    exit
    ;;
esac
case "$win_name" in
  *'Internet Bank'*|*'YouTube'*|MPlayer|Netflix*|Prime\ Video*)
    exit
    ;;
esac

tmpfilename="$RAMTMP/screenlog-capture.png"
scrot -buq 0 "$tmpfilename"
if [ ! -s "$tmpfilename" ]
then
  exit
fi
if [ $(stat -c %s "$tmpfilename") -lt 500000 ]
then
  mogrify -depth 3 "$tmpfilename"
else
  mogrify -type Grayscale -depth 3 "$tmpfilename"
fi
latest="$rootdir/latest.png"
puzzle-diff -c -e -E 0.1 "$latest" "$tmpfilename" &>/dev/null
if [ $? -eq 10 ]
then
  # No relevant changes, don't keep screenshot
  rm "$tmpfilename"
else
  win_name="$(printf %.30s $win_class) - $(printf %.60s $win_name)"
  date=$(date '+%Y-%m/%Y-%m-%d')
  dirname="$rootdir/$date"
  mkdir -p "$dirname"
  filename="$dirname/$(date '+%H.%M.%S') $win_name.png"
  mv "$tmpfilename" "$filename"
  rm -f "$latest"
  ln -s "$filename" "$latest"
fi

Some of the interesting features:

• It uses scrot to take screenshots.
• It includes the name of the current window in the filename, making lookup easier.
• It does not run if the screensaver is running (this is Cinnamon-specific, other desktops will need a different command to check for the screensaver state).
• It filters out some applications I don't want to take screenshots of, this list can be easily extended.
• It stops taking screenshots if disk usage goes above 98%.
• It uses puzzle-diff to skip saving a screenshot if it would be the same as the previous one (with some tolerance).
• It radically reduces the color depth of the screenshots (or even makes them grayscale, depending on the size) to save disk space.
• I use a RAM disk for intermediate storage (before deciding whether to keep an image), but you can use the regular /tmp location as well.

I use another shell script, screenlog, to call this one periodically:

#! /bin/bash
while true
do
  sleep 5
  screenlog-capture
done

I came up with

#! /usr/bin/env bash

sleep_period=30s

while true; do

scrot $HOME/Pictures/"$(date +%Y%m%d%H%M%S)".png

sleep ${sleep_period}
done

I have ~/bin and so I saved this script there as continuous-scrot.sh and made it executable. To run it, I open a terminal window and type the name of the script and press Enter. I leave this terminal window active and full-screen screenshots are captured every 30s in your ~/Pictures folder. To stop, just go back to this terminal window and press Ctrl+C.

Since I have many linux distributions where I need screenshots, and they use various window managers I use probably the oldest of screenshot utilities xwd. It is a part of XServer distribution, so I can be sure it is installed every time. I am not sure if it is distributed and if it works with wayland. The command

xwd -display :0.0 -root -out screenshot.xwd

should make a screenshot of root window of display :0.0. The output file is a special formatted dump file. ImageMagick can convert that file to some more common format. For more information: https://linux.die.net/man/1/xwd.

You can find many ideas how to run such utility on regular intervals in other answers. To make output to a different file every time you could do:

xwd -display :0.0 -root -out "$(date).xwd"

The first thing I can think about is to open a terminal and use it to issue scrot within a while with a sleep. Something like this:

while sleep 30; do scrot <whatever>; done

To me, there's a catch in this. What if you make something significant between the 30 secs interval? Have you considered a screen recorder (SimpleScreenRecorder is one available on ubuntu distribution. another name I recall is Istanbul)

I'd use recordmydesktop, possibly with a low fps rate and no audio to reduce the amount of data recorded.

While these are not exactly screenshots, but a full video, the advantage is that you get good compression as only differences between consecutive images need to be saved, you have the option of also recording your microphone so you can take notes by speaking, and you can optionally add start/stop buttons to the system notification area.

How I solved this for myself:

First, install the following cronjob:

* * * * * DISPLAY=:0 /usr/bin/sudo -i -u <USER> bash -c '/home/<USER>/bin/create-screenshot.sh; sleep 30; /home/<USER>/bin/create-screenshot.sh;'

Notice the DISPLAY=:0 statement to allow cron to access the X Server.

Then, create ~/bin/create-screenshot.sh with the following contents:

#!/bin/bash

user="<USER>"
folder="$(date +%Y%m%d)"
y="$(date +%Y)"
m="$(date +%m)"

mkdir -p "/home/$user/screenshots/$y/$m/$folder"
file="$(date +%Y%m%d%H%M%S)".png
path="/home/$user/screenshots/$y/$m/$folder/$file"
scrot $path