LINUX

🔥 Learn About Commands 🔥

Cheatsheet of Linux

Command	Description
man <tool>	Opens man pages for the specified tool.
<tool> -h	Prints the help page of the tool.
apropos <keyword>	Searches through man pages' descriptions for instances of a given keyword.
cat	Concatenate and print files.
whoami	Displays current username.
id	Returns users identity.
hostname	Sets or prints the name of the current host system.
uname	Prints operating system name.
pwd	Returns working directory name.
ifconfig	The ifconfig utility is used to assign or view an address to a network interface and/or configure network interface parameters.
ip	Ip is a utility to show or manipulate routing, network devices, interfaces, and tunnels.
netstat	Shows network status.
ss	Another utility to investigate sockets.
ps	Shows process status.
who	Displays who is logged in.
env	Prints environment or sets and executes a command.
lsblk	Lists block devices.
lsusb	Lists USB devices.
lsof	Lists opened files.
lspci	Lists PCI devices.
sudo	Execute command as a different user.
su	The su utility requests appropriate user credentials via PAM and switches to that user ID (the default user is the superuser). A shell is then executed.
useradd	Creates a new user or update default new user information.
userdel	Deletes a user account and related files.
usermod	Modifies a user account.
addgroup	Adds a group to the system.
delgroup	Removes a group from the system.
passwd	Changes user password.
dpkg	Install, remove and configure Debian-based packages.
apt	High-level package management command-line utility.
aptitude	Alternative to apt.
snap	Install, remove and configure snap packages.
gem	Standard package manager for Ruby.
pip	Standard package manager for Python.
git	Revision control system command-line utility.
systemctl	Command-line based service and systemd control manager.
ps	Prints a snapshot of the current processes.
journalctl	Query the systemd journal.
kill	Sends a signal to a process.
bg	Puts a process into background.
jobs	Lists all processes that are running in the background.
fg	Puts a process into the foreground.
curl	Command-line utility to transfer data from or to a server.
wget	An alternative to curl that downloads files from FTP or HTTP(s) server.
python3 -m http.server	Starts a Python3 web server on TCP port 8000.
ls	Lists directory contents.
cd	Changes the directory.
clear	Clears the terminal.
touch	Creates an empty file.
mkdir	Creates a directory.
tree	Lists the contents of a directory recursively.
mv	Move or rename files or directories.
cp	Copy files or directories.
nano	Terminal based text editor.
which	Returns the path to a file or link.
find	Searches for files in a directory hierarchy.
updatedb	Updates the locale database for existing contents on the system.
locate	Uses the locale database to find contents on the system.
more	Pager that is used to read STDOUT or files.
less	An alternative to more with more features.
head	Prints the first ten lines of STDOUT or a file.
tail	Prints the last ten lines of STDOUT or a file.
sort	Sorts the contents of STDOUT or a file.
grep	Searches for specific results that contain given patterns.
cut	Removes sections from each line of files.
tr	Replaces certain characters.
column	Command-line based utility that formats its input into multiple columns.
awk	Pattern scanning and processing language.
sed	A stream editor for filtering and transforming text.
wc	Prints newline, word, and byte counts for a given input.
chmod	Changes permission of a file or directory.
chown	Changes the owner and group of a file or directory.

Bash Shell Scripting

#! /usr/bin/bash

echo hello bash me is Ritesh 😎.

TEMP="some data"
echo "this is some : $TEMP"

# get values from the user

read -p "enter something : " INP
echo "you entered $INP"

# #if else statements

if [ $INP -eq 100 ]
then
    echo "you are awesome"
elif [ "$INP" == "Rish" ]
then
    echo "you are awesome too"
else
    echo "get lost"
fi

# -eq equal
# -ne not equal
# -gt greater than
# -ge greater than or equal to
# -lt less than
# -le less than or equal to


# lets make programme number 1 🎃

# addition of two numbers

read -p "enter number 1: " NUM1
read -p "enter number 2: " NUM2
((SUM=$NUM1+$NUM2))
echo "the sum of the numbers is $SUM"

# lets make programme number 2 👓

# highest of three numbers

read -p "enter number 1: " NUM1
read -p "enter number 2: " NUM2
read -p "enter number 3: " NUM3
if((NUM1>NUM2));then
    if((NUM1>NUM3));then
        echo "the greatest is $NUM1"
    else
        echo "the greatest is $NUM3"
    fi
elif((NUM2>NUM3));then
    echo "the gratest is $NUM2"
else
    echo "the greatest is $NUM3"
fi

# lets make programme number 3 🥼

# swap two numbers

read -p "enter number 1: " NUM1
read -p "enter number 2: " NUM2
((NUM1=$NUM1+$NUM2))
((NUM2=$NUM1-$NUM2))
((NUM1=$NUM1-$NUM2))
echo "after swap $NUM1 and $NUM2"

For Loops
NAME="hello bash me is Ritesh 😎"
for var in $NAME
do
    echo $var
done

while 

N=10
while((N!=0))
do 
    echo $N
    ((N--))
done

# lets make programme number 4 🎓

# prime number

read -p "enter a number to check: " N
I=2
P="prime"
while((I<N))
do
    if((N%I==0))
    then
        P="not prime"
        break
    fi
done
echo $P

# programme number 5 🧐
# even odd

# Do it by yourself 😉
read var
if(($var%2==0));then
    echo "even"
else
    echo "odd"
fi


# programme number 6 🎂
# sum of digits 

read -p "enter a number: " N
S=0
while((N!=0))
do
    ((T=$N%10))
    ((N=$N/10))
    ((S=$S+$T))
done
echo $S

#! /usr/bin/bash
for var in "$@"
do
    echo $var
done


echo $#

((n=$1+$2))
echo $$
echo $n

n=1
while((n!=6))
do
    mkdir dir-$n
    cd dir-$n
    touch file-$n
    cd ..
    ((n++))
done

#! /usr/bin/bash
x=3;y=5;z=10;
if [ ($x -eq 3 ) -a ( $y -eq 5 -o $z -eq 10 ) ]
then
    echo $x
else
    echo $y
fi