mjhjmtu

For changing a specific image's size I use the following command:

mogrify -geometry x50 my_image.png

Every time that I take a new print screen, an image is saved on my ~/Pictures folder. I'd like to make a script that watches my Pictures folder and takes an action copying a reduced sized version of my new image to a different folder on my computer, e.g. ~/.icons/...

I know I could solve this problem using cron, but I don't really want to take actions at regular intervals of time. I want a command ( or a script) that can find out what's different on a folder based on logs or something like this. Is that possible? How can I do it?

I've created this functional script that solves my problem using inotify-tools. So I'm leaving it here in case it's useful for someone else.

#!/bin/bash

watchedFolder=~/Pictures
iconsFolder=~/.icons
imageGeometry=100

while [ true ]
do
 fileName=$(inotifywait -q -e create --format "%f" "$watchedFolder")
 if ! [ -d $iconsFolder ]; then mkdir -p $iconsFolder ; fi
 sleep 1s
 cp $watchedFolder/"$fileName" $iconsFolder
 mogrify -geometry x$imageGeometry $iconsFolder/"$fileName"
done

Save it as e.g. ~/automatedIcons.bash and make it executable with chmod +x ~/automatedIcons.bash. Now if you run it, it's already working, it's going to copy every new picture that is created inside the Pictures folder to a new location and change its size. To make it run on boot use crontab -e and write one line with the script's location on it, e.g. @reboot /home/myUserName/automatedIcons.bash.

This is just a functional script. So if anyone has any suggestion about improving the way it works, feel free to write in the comments.

This question (or similar) was answered in Stack Overflow

Mainly says, that you need to use inotify-tools

I've created a script that simplifies the use of inotifywait by declaring specific flags that can be used later. So I'm posting it here as well:

#!/bin/bash

watchedFolder=/path/to/monitored_folder

declare -A cache
inotifywait --format="%w^%e^%f" -q -r -m -e move,create,delete "$watchedFolder" |
while IFS='^' read id event file; do
 file_moved_from_different_folder='0'
 file_renamed='0'
 file_moved_different_folder='0'
 file_created='0'
 file_deleted='0'

 echo ""
 echo "id:$id"
 echo "event:$event"
 echo "file:$file"

################# DECLARATION OF FLAGS
 if [ "$event" == "MOVED_FROM" -o "$event" == "MOVED_FROM,ISDIR" ]; then
 cache[moved_from]="$file"
 SECONDS=0
 elif [ "$event" == "MOVED_TO" -o "$event" == "MOVED_TO,ISDIR" ]; then
 if [ $SECONDS -gt 2 ]; then
 echo "Action: Moved from an external folder flag declared"
 file_moved_from_different_folder='1'
 elif [ "$cache[moved_from]" != "$file" ]; then
 echo "Action: Renamed Flag declared ..."
 file_renamed='1'
 unset cache[moved_from]
 elif [ "$cache[moved_from]" == "$file" ] ; then
 echo "Action: Moved to a different folder flag declared"
 file_moved_different_folder='1'
 unset cache[moved_from]
 fi
 elif [ "$event" == "CREATE" -o "$event" == "CREATE,ISDIR" ]; then
 echo "Action: Created Flag declared ..."
 file_created='1'
 elif [ "$event" == "DELETE" -o "$event" == "DELETE,ISDIR" ]; then
 echo "Action: Deleted Flag declared ..."
 file_deleted='1'
 fi
###

if [ $file_moved_from_different_folder == '1' ]; then
 echo "Do something here when a file from outside is moved to the monitored folder"
fi

if [ file_renamed == '1' ]; then
 echo "Do something here when a file is renamed"
fi

if [ $file_moved_different_folder == '1' ]; then
 echo "Do something here when files are moved inside the recursive structure of the monitored folder"
fi 

if [ $file_created == '1' ]; then
 echo "Do something here when a file is created"
fi 

if [ $file_deleted == '1' ]; then
 echo "Do something here when a file is deleted"
fi

done

The idea here is to separate flags that can tell us what's happening in a folder while saving the path of the file ($id), the event that's happening ($event) and the name of the file ($file) on variables for later use. Besides the fact that we can easily detect when a file or folder is renamed (the renamed flag can't be got directly using inotifywait).

In this example, the recursive parameter -r is settled, so the script is going to watch all subfolders of the watched folder as well. For watching only a single folder just remove the -r parameter... This is a generic solution that can be used for different situations when we want to execute specific actions based on changes that are happening on folders.