The usefull linux commands

How to find and delete logs file MORE THAN 30 DAYS OLD

# find /path/to/log/ -type f -name \*.log\* -mtime +30 -exec rm {} \; > /dev/null 2>&1

How to find and delete logs file LESS THAN 30 DAYS OLD

# find /path/to/log/ -type f -name \*.log\* -mtime -30 -exec rm {} \; > /dev/null 2>&1

How to one-liner that allows to create a directory and move into it at the same time.

# mkdir test-dir && cd $_

How to display size of folder.

#du -csbh /path/to/folder

How to display output as a table

# cat /etc/passwd | column -t -s: 

Run last command as root

# sudo !!

Return to previous directory

# cd -

How to add passphrase into id_rsa file use ssh-keygen command

#ssh-keygen -f id_rsa -p

How to combine wget and tar in one command

# wget -qO- http://link-download | tar xvz

How to combine find and xargs command

# find /home/huupv -name *.jpg | xargs -d '\n' ls -ll

grep command regurar expression match all IP address in a log file

grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b"

how to check file duplicate

find /home/huupv/ -type f -print0 | xargs -0 md5sum | sort | uniq -D -w 32

How to determining own ip public 

curl ipinfo.io/ip

or

curl -s checkip.dyndns.org | sed -e 's/.*Current IP Address: //' -e 's/<.*$//'