Learn Python & Linux

Lecture: Introduction to Linux Bash and Python

Linux Bash Basics

Display the current directory:

pwd

List files and directories:

ls

Change directory:

cd <directory_name>

Create a new directory:

mkdir <directory_name>
# if you want to add nested folders
mkdir -p /this/is/nested

Remove a directory:

	rmdir <directory_name>
	# or you can remove recursivly using 
	rm -rf

Copy a file:

cp <source_file> <destination_file>

Move a file:

mv <source_file> <destination_file>

Print the contents of a file:

cat <file_name>

Search for a specific string in a file:

grep <search_string> <file_name>

Count the number of lines in a file:

wc -l <file_name>

Find and replace text in a file:

sed 's/<old_text>/<new_text>/g' <file_name>

Check disk usage of a directory:

du -sh <directory_name>

Display system information:

uname -a
# or 
cat /etc/os-release
128.4.121.165 ==> internal
?? ==> external

Calendar

The cal command is used to display a calendar. When used without any arguments, it displays the current month's calendar. If a specific year is provided as an argument, it displays the calendar for that year.

cal 
cal 2019

The bc command is a command-line calculator that allows you to perform mathematical calculations in the Linux command line. It provides functionalities for basic arithmetic operations, advanced mathematical functions, and variable assignment.

bc 
198 * 2 
x= 22
y= 33
(x*2)+(y*2)

whatis

The whatis command in Linux is used to display a short description of a given command. It provides a brief explanation of the purpose or functionality of the specified command.

whatis grep 
whatis sudo
...

The who command in Linux is used to display information about the users who are currently logged in to the system. It provides details such as the username, terminal, login time, and IP address of the logged-in users.

who
# or 
w

echo

The echo command is used in Linux to display a line of text or a variable value on the terminal. It is commonly used for printing messages or variables in shell scripts or on the command line. When used with the -e option, it can also interpret backslash escapes.

For example:

echo "Hello, World!"

This will output "Hello, World!" on the terminal.

You can also use variables with echo:

name="John"
echo "Hello, $name!"

This will output "Hello, John!" on the terminal.

head The term head can have multiple meanings depending on the context. It can refer to the part of the body that contains the brain and sensory organs, or it can be used to describe a person who is in charge or a leader of a group. It can also refer to the top or frontmost part of something, such as the head of a bed or the head of a company.
Tail

The term "tail" has multiple meanings depending on the context. In the context of animals, it refers to the elongated rear end of certain animals. In the context of clothing, it refers to a trailing or hanging part at the back of a garment. In the context of data or logs, "tail" refers to a command or function that displays the last few lines or entries.

Some other commands to explore later:

passwd
history
kill
sort
touch
uniq
wc
sleep

Python Basics

Print "Hello, World!":

print("Hello, World!")

Variables and data types:

name = "John"
age = 25
is_student = True

Math operations:

x = 5
y = 3
sum = x + y
difference = x - y
product = x * y
quotient = x / y

String manipulation:

message = "Hello, World!"
print(message.upper())
print(message.lower())
print(len(message))

Lists and indexing:

fruits = ["apple", "banana", "orange"]
print(fruits[0])
print(fruits[1:])

Conditional statements:

x = 10
if x > 5:
    print("x is greater than 5")
else:
    print("x is less than or equal to 5")

Loops:

for i in range(5):
    print(i)

Functions:

def greet(name):
    print("Hello, " + name + "!")

greet("Alice")

File handling:

file = open("data.txt", "w")
file.write("Hello, World!")
file.close()

Error handling:

try:
    x = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")