$ iconv -f CP1252 -t UTF8 inputfile.txt -o outputfile.txt
Or
$ enconv -x UTF8 somefile.txt

$ enconv -d somefile.txt
Or
$ file -i somefile.txt

$ awk '{ gsub("\\x1B\\[[0-?]*[ -/]*[@-~]", ""); print }' somefile.txt

input.txt: ASCII text
VS
input.txt: ASCII text, with CRLF line terminators

$ awk '{ sub("\r$", ""); print }' input.txt > output.txt
Or
$ dos2unix input.txt

$ awk 'sub("$", "\r")' input.txt > output.txt
Or
$ unix2dos input.txt

$ netstat -anlp | grep LIST
$ ss -nlpt | grep LIST

$ wget -q -O - https://ipinfo.io/ip

Start:
CTRL + ALT + F1-6
​
Stop:
ALT + F8

$ ps aux | grep firefox
Or
$ pidof firefox
​
$ kill -15 <PID>
Or
$ kill -SIGTERM <PID>
Or
$ kill <PID>
​
If -15 signal didn't help, use stronger -9 signal:
$ kill -9 <PID>
Or
$ kill -SIGKILL <PID>

$ openssl enc -e -aes-128-ecb -in file.txt -out file.txt.ecb -K 10101010
$ openssl enc -d -aes-128-ecb -in file.txt.ecb -out file.txt.ecb_dec -K 10101010
​
$ echo 'secret_data1 + secret_data2 + secret_data3' | openssl enc -e -aes-256-cbc -a -salt -md sha256 -iv 10101010 -pass pass:qwerty
$ echo 'U2FsdGVkX1+d1qH1M3nhYFKscrg5QYt+AlTSBPHgdB4JEP8YSy1FX+xYdrfJ5cZgfoGrW+2On7lMxRIhKCUmWQ==' | openssl enc -d -aes-256-cbc -a -salt -md sha256 -iv 10101010 -pass pass:qwerty

$ ssh-keygen -t rsa -b 4096 -N 's3cr3t_p4ssw0rd' -C '[email protected]' -f rsa_key
$ mv rsa_key rsa_key.old
$ openssl pkcs8 -topk8 -v2 des3 \
  -in rsa_key.old -passin 'pass:s3cr3t_p4ssw0rd' \
  -out rsa_key -passout 'pass:s3cr3t_p4ssw0rd'
$ chmod 600 rsa_key
​
$ openssl rsa -text -in rsa_key -passin 'pass:s3cr3t_p4ssw0rd'
$ openssl asn1parse -in rsa_key
​
$ ssh-keygen -o -a 100 -t ed25519 -f ~/.ssh/id_ed25519

$ gpg --list-keys

$ gpg --full-generate-key [--expert]

$ gpg --output revoke.asc --gen-revoke [email protected]
revoke.asc

$ gpg --armor --output user.pub --export [email protected]
user.pub

$ gpg --import recipient.pub

$ gpg -o/--output encrypted.txt.gpg -e/--encrypt -s/--sign -u/--local-user [email protected] -r/--recipient [email protected] plaintext.txt
encrypted.txt.gpg

$ gpg --list-only -v -d/--decrypt encrypted.txt.gpg

$ gpg --verify signed.txt.gpg
$ gpg --verify signed.txt.sig signed.txt

$ gpg -o/--output decrypted.txt -d/--decrypt --try-secret-key [email protected] encrypted.txt.gpg
$ gpg -o/--output decrypted.txt -d/--decrypt -u/--local-user [email protected] -r/--recipient [email protected] encrypted.txt.gpg

$ > logfile
Or
$ cat /dev/null > logfile
Or
$ dd if=/dev/null of=logfile
Or
$ truncate logfile --size 0

$ cat /dev/null > ~/.bash_history && history -c && exit

$ shred -zvu -n7 /path/to/file
$ find /path/to/dir -type f -exec shred -zvu -n7 {} \\;
$ shred -zv -n0 /dev/sdc1

$ lsblk
$ sudo fdisk -l
$ df -h

$ sudo fdisk /dev/sd??

$ sudo umount /dev/sd??
$ sudo mkfs.<type> -F 32 -I /dev/sd?? -n VOLUME-NAME
type: 'msdos' (=fat32), 'ntfs'

$ mcopy -i floppy.img 123.txt ::123.txt
$ mdel -i floppy.img 123.TXT

$ md5sum /path/to/abc.txt | awk '{print $1, "/path/to/cba.txt"}' > /tmp/checksum.txt
$ md5sum -c /tmp/checksum.txt

$ hashdeep -c md5 -r /path/to/dir1 > dir1hashes.txt
$ hashdeep -c md5 -r -X -k dir1hashes.txt /path/to/dir2

$ find . -type f -exec chmod 644 {} \;

$ find . -type d -exec chmod 755 {} \;

$ sudo crontab -l | { cat; echo '@reboot echo $((16*1024*1024)) > /proc/sys/vm/dirty_background_bytes'; } | crontab -
$ sudo crontab -l | { cat; echo '@reboot echo $((48*1024*1024)) > /proc/sys/vm/dirty_bytes'; } | crontab -

$ dpkg -l linux-image-\* | grep ^ii
$ kernelver=$(uname -r | sed -r 's/-[a-z]+//')
$ dpkg -l linux-{image,headers}-"[0-9]*" | awk '/ii/{print $2}' | grep -ve $kernelver
$ sudo apt-get purge $(dpkg -l linux-{image,headers}-"[0-9]*" | awk '/ii/{print $2}' | grep -ve "$(uname -r | sed -r 's/-[a-z]+//')")

$ sudo apt update
$ sudo apt upgrade -y
$ sudo apt install xfce4 xfce4-terminal gtk2-engines-pixbuf -y

$ sudo apt install peek -y
Or
$ sudo apt install byzanz xdotool -y
$ xdotool getmouselocation
$ byzanz-record --duration=15 --x=130 --y=90 --width=800 --height=500 ~/Desktop/out.gif

$ sudo apt purge ntp -y
$ sudo timedatectl set-timezone Europe/Moscow
$ sudo vi /etc/systemd/timesyncd.conf
NTP=0.ru.pool.ntp.org 1.ru.pool.ntp.org 2.ru.pool.ntp.org 3.ru.pool.ntp.org
$ sudo service systemd-timesyncd restart
$ sudo timedatectl set-ntp true
$ timedatectl status
$ service systemd-timesyncd status
$ service systemd-timedated status

$ convert img1.png img2.png -fx "(((255*u)&(255*(1-v)))|((255*(1-u))&(255*v)))/255" img_out

tar -cvf directory.tar directory

tar -xvf directory.tar

tar -cvzf directory.tar.gz directory

tar -xvzf directory.tar.gz

tar -cvjf directory.tar.bz directory

tar -xvjf directory.tar.bz

$ scp [-P 2222] file.txt [email protected]:/remote/directory

$ scp [-P 2222] [email protected]:/remote/file.txt /local/directory

$ 7z a packed.7z -mhe -p"p4sSw0rD" *

$ 7z e packed.7z -p"p4sSw0rD"

$ grep -nwr 'pattern' /path/to/dir

$ find . -type f -name "*.txt" -exec sed -i'' -e 's/\<foo\>/bar/g' {} +

$ find . -type f -print -exec sh -c 'strings $1 | grep -i -n "signature"' sh {} \;

$ find . -type f -print0 | xargs -0 grep <PATTERN>

$ readlink -f somefile.txt

$ paste -d':' a.txt b.txt > c.txt

$ dpkg -s <package_name>
$ dpkg-query -W -f='${Status}' <package_name>
$ OUT="dpkg-query-$(date +'%FT%H%M%S').csv"; echo 'package,version' > ${OUT} && dpkg-query -W -f '${Package},${Version}\n' >> ${OUT}

 # Mount volume
$ veracrypt -t --pim=0 --keyfiles='' --protect-hidden=no /home/snovvcrash/SecretVolume.dat /mnt
 # Unmount all
$ veracrypt -d

$ sudo openconnect --protocol=gp gp.megacorp.com -u snovvcrash

$ script ~/ws/shells/`date "+%FT%H%M%S"`.script

bash ~/.tmux/plugins/tmux-logging/scripts/screen_capture.sh
bash ~/.tmux/plugins/tmux-logging/scripts/save_complete_history.sh

PS1='${debian_chroot:!($debian_chroot)}[\D!d}|\D{!k:!M}] \[\033[01;32m\]λ  \[\033[00m\]\[\033[01;34m\]\w\[\033[00m\] '

PROMPT="!(?:!{$fg_bold[green]!}➜ :!{$fg_bold[red]!}➜ ) "
PROMPT+='!{$fg[cyan]!}!(4~|!-1~/…/!2~|!3~)!{$reset_color!} $(git_prompt_info)'
​
if lsof -tac script "$(tty)" > /dev/null; then
    PROMPT="[!D{!d}|!D{!k:!M}]* $PROMPT"
else
    PROMPT="[!D{!d}|!D{!k:!M}] $PROMPT"
fi

 # PHP
$ sudo add-apt-repository ppa:ondrej/php -y
$ sudo apt update
$ sudo apt install php7.2 -y
$ sudo apt install php7.2-curl php7.2-gd php7.2-json php7.2-mbstring -y
​
 # Apache
$ sudo apt install apache2 libapache2-mod-php7.2 -y
$ sudo service apache2 restart
​
 # MySQL
$ sudo apt install mysql-server php7.2-mysql
$ sudo mysql_secure_installation
$ service mysql restart
​
 # Test
$ sudo sh -c 'echo "<?php phpinfo(); ?>" > phpinfo.php'
-> http://127.0.0.1/phpinfo.php

$ sudo apt-get install cmatrix

$ wget -O screenfetch https://raw.github.com/KittyKatt/screenFetch/master/screenfetch-dev
$ chmod +x screenfetch
$ sudo mv screenfetch /usr/bin