✨What are Linux Commands?

Linux commands are a set of instructions that can be executed in a Unix-like operating system (such as Linux, macOS, or FreeBSD) to perform various tasks, such as managing files, directories, processes, users, and system settings.

Linux commands can be used to perform a wide range of tasks, such as file management, text processing, system configuration, network operations, and more.

✨ Linux Commands By Category

1. File Management Commands

File Management Commands allow you to perform various operations on files and directories. Here are some commonly used file management commands:

ls: List the files and directories in a directory on the file system,
cd: Change the current working directory.
pwd: Print the current working directory.
mkdir: Create a new directory.
rmdir: Remove directory.
touch: Create a new file.
cat: Prints the contents of a file.
rm: Used to Remove (delete) files or directories from the file system.
cp: Used to copy files or directories from one location to another.
mv: Used to rename files or directories, as well as move them from one location to another.
chmod: Change the permissions (i.e., access permissions) of files and directories.
chown: Change the ownership of files and directories
find: The find command in UNIX is a command line utility for walking a file hierarchy. It can be used to find files and directories and perform subsequent operations on them. It supports searching by file, folder, name, creation date, modification date, owner, and permissions. By using the ‘-exec’ other UNIX commands can be executed on files or folders found.
locate: The locate command is a Unix utility used for quickly finding files and directories. The command is a more convenient and efficient alternative to the find command, which is more aggressive and takes longer to complete the search.

Opposite to find, the locate command doesn't search the entire filesystem but looks through a regularly updated file database in the system. Thus, the search is completed much faster.

2. Text Processing Commands

Text processing commands are used for manipulating and processing text files or streams of text data. Here are some common text-processing commands:

grep: Search for patterns in files
sed: Stream editor for text manipulation
awk: Text processing tool for pattern matching and data extraction
sort: Sort lines of text
uniq: Report or omit repeated lines
cut: Remove sections from each line of a file
head: Display the first line of the files
tail: Display the last line of the files
more: The more command lets you view text files in your terminal one screen page at a time.
less: Less command is used to read the contents of a text file one page (one screen) at a time with navigation. It has faster access because if the file is large, it doesn’t access the complete file, but accesses it page by page.
wc: Count lines, words, and characters in files

3. System Management Commands

System management commands are used for managing various aspects of the system, including system configuration, process management, user management, and system monitoring. Here are some common system management commands:

ps: Display process status
top: Display system processes in real-time
df: Display disk space usage
du: Estimate file space usage
free: Display memory usage
uname: Display system information
shutdown: Shut down or reboot the system
su: Switch user or become superuser

4. Network Commands

Network commands are used for managing various aspects of networking, such as network configuration, network diagnostics, and network troubleshooting. Here are some common network commands:

ping: Test network connectivity
ifconfig: Configure network interfaces
netstat: Display network connections and statistics
nslookup: Query DNS for domain information
traceroute: Display the route and measure transit delays of packets
ssh: Securely connect to remote servers
scp: Securely copy files between local and remote systems
ftp: Transfer files to/from a remote server using FTP

5. User Management Commands

User management commands are used for creating, modifying, and managing user accounts, as well as setting user permissions and privileges. Here are some common user management commands:

useradd: Add a new user account
userdel: Delete a user account
passwd: Change user password
chsh: Change user shell
chage: Configure password expiration and account aging
id: Display user and group information
su: Switch user or become superuser
sudo: Execute commands with superuser or other user privileges

✨ Some of the examples of Linux Commands

Check your present working directory

 pwd - command will show you the current working directory in which 
 you are working.

List all the files or directories including hidden files

 ls - command is used to list the contents of a file and directory.
 ls -la - command list all including hidden files and directory.

Create a nested directory X/Y/Z

 mkdir - command is used to make a new folder in a specific location
 mkdir -p  X/Y/Z - command create nested directory

To view what's written in a file

 cat - command is used to print the contents of the file
 syntax - cat <filename?
 e.g cat file.txt

To change the access permissions of file

 chmod - command is used to change the permission of the file & 
 directory
 syntax - chmod <permission> <filename>
 e.g chmod 644 file.txt

To check which commands you have run till now

 history - command is used to display commands you have executed
 the terminal

To remove a Directory / Folder

 There are two main commands are used to delete folders in Linux
 rmdir - command is used to delete empty folder
 rm - command is used to delete empty and non empty folder
 for eg. rmdir empty_folder_name
         rm -d empty_folder_name
         rm -r non_empty_folder_name

To create a txt file and to view the content

 touch - command is used to create an empty file
 cat - command is used to view its content

Add content in devops.txt (One in each line) - Apple, Mango, Banana, Cherry, Kiwi, Orange, Guava

 vim - command is used to edit the file in linux and add a content
 into it.
 for e.g vim devops.txt
 press i to enter into insert mode then insert the data as per
 requirements 
 i.e 
 Apple
 Mango
 Banana
 Cherry
 Kiwi
 Orange
 Guava

To Show only top three fruits from the file

head - command is used to display first 10 lines of the file
for e.g head -n 3 filename.txt

To Show only bottom three fruits from the file

tail - command is used to display last 10 lines of the file
for e.g tail -n 3 filename.txt

Create a Colors.txt file and Add content in Colors.txt file(One in each line) - Red, Pink, White, Black, Blue, Orange, Purple, Grey

vim - command is used to edit the file in linux and add a content
into it.
for e.g vim Colors.txt
press i to enter into insert mode then insert the data as per
requirements 
i.e 
Red
Pink
White
Black
Blue
Orange
Purple

To find the difference between fruits.txt and Colors.txt file

diff - command to compare two text files and see the differences
example:  diff devops.txt Colors.txt
It will output all lines that are different between the two files

Thank you for reading. I hope you will find this article helpful. if you like it please share it with others

Mohd Ishtikhar Khan : )

🚀Day 03- Essential Linux Commands

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