Tag: linux

You can do this with inotifywait utility from inotify-tools package

while true ; do
  inotifywait -e delete_self "/tmp/fileToMonitor.txt" \
    && cp new_file "/tmp/fileToMonitor.txt"
done

[ "$UID" -eq 0 ] || exec sudo "$0" "$@"

while true ; do
  inotifywait -e modify "/etc/resolv.conf" && ./dns.sh
done

References
https://superuser.com/questions/939600/how-to-get-notified-when-a-specific-file-is-deleted-in-linux
https://superuser.com/questions/181517/how-to-execute-a-command-whenever-a-file-changes
http://man7.org/linux/man-pages/man1/inotifywait.1.html#EVENTS

Text between backticks is executed and replaced by the output of the command (minus the trailing newline characters, and beware that shell behaviors vary when there are NUL characters in the output). That is called command substitution because it is substituted with the output of the command.

A=`cat /etc/p2ass2wd2 | head -n1`
echo "$A"

A=$(cat /etc/p2ass2wd2 | head -n1)
echo "$A"

References
https://unix.stackexchange.com/questions/48392/understanding-backtick
https://unix.stackexchange.com/questions/147420/what-is-in-a-command

Displaying private IP addresses

ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | cut -f1  -d'/'

address=$(ip addr show wlp3s0 | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | cut -f1  -d'/')

Displaying the public IP address

If you want to know the public IP address of a Linux server, you can send an HTTP request to one of the following web servers.

• http://ifconfig.me
• http://www.icanhazip.com
• http://ipecho.net/plain
• http://indent.me
• http://bot.whatismyipaddress.com
• https://diagnostic.opendns.com/myip
• http://checkip.amazonaws.com

curl http://checkip.amazonaws.com

wget -qO- http://checkip.amazonaws.com

References
https://unix.stackexchange.com/questions/119269/how-to-get-ip-address-using-shell-script
https://www.linuxtrainingacademy.com/determine-public-ip-address-command-line-curl/