run script at startup of ubuntu

Run script at startup (when you login). Following example add a small memory check script at the startup

1.  cd  /usr/share/applications
2. sudo gedit  memcheck.desktop

[Desktop Entry]
Name=memcheck
Comment=memcheck  Tool
Exec=/home/***/projects/mem_alert/memcheck.sh
Terminal=true
Type=Application
Icon=someicon copied from existing .desktop files in same folder

3. Open tweaks

4. Click "startup applications"
5. Click add, then select "memcheck" application from the list. If it do not appear then you have done some thing wrong.
6. Now logout and login. The mem check script should run after user login

My memcheck.sh looks like:

#!/bin/bash
#Minimum available memory limit, MB
THRESHOLD=2000
#Check time interval, sec
INTERVAL=30
while :
do
    free=$(free -m|awk '/^Mem:/{print $4}')
    buffers=$(free -m|awk '/^Mem:/{print $6}')
    cached=$(free -m|awk '/^Mem:/{print $6}')
    available=$(free -m|awk '/^Mem:/{print $7}')
    message="Free $free""MB"", buffers $buffers""MB"", cached $cached""MB"", available $available""MB"""
    if [ $available -lt $THRESHOLD ]
        then
        notify-send "Memory is running out!" "$message"
    fi
    echo $message
    sleep $INTERVAL
done