Here are 50 Linux commands that every developer should know, along with a brief description and an example of each command:

ls - Lists the contents of a directory.
- Example: ls will list the contents of the current directory. ls /usr/local will list the contents of the /usr/local directory.
pwd - Prints the current working directory.
- Example: pwd will print the full path of the current working directory.
cd - Changes the current working directory.
- Example: cd /usr/local will change the current working directory to /usr/local.
mkdir - Creates a new directory.
- Example: mkdir mydir will create a new directory called mydir.
mv - Moves a file or directory.
- Example: mv file.txt /usr/local/ will move the file file.txt to the /usr/local directory.
cp - Copies a file or directory.
- Example: cp file.txt /usr/local/ will copy the file file.txt to the /usr/local directory.
rm - Removes a file or directory.
- Example: rm file.txt will remove the file file.txt, while rm -r mydir will remove the directory mydir and all of its contents.
touch - Creates a new empty file.
- Example: touch file.txt will create a new empty file called file.txt.
ln - Creates a link to a file or directory.
- Example: ln -s /usr/local/file.txt file.txt will create a symbolic link to /usr/local/file.txt called file.txt in the current directory.
cat - Displays the contents of a file.
- Example: cat file.txt will display the contents of the file file.txt in the terminal.
clear - Clears the terminal screen.
- Example: clear will clear the contents of the terminal screen.
echo - Prints a message to the terminal.
- Example: echo "Hello, world!" will print the message "Hello, world!" to the terminal.
less - Views a file with pagination.
- Example: less file.txt will allow you to view the contents of file.txt one page at a time.
man - Displays the manual page for a command.
- Example: man ls will display the manual page for the ls command, which describes its usage and options.
uname - Displays information about the current system.
- Example: uname -a will display all information about the current system, including the kernel version and machine hardware name.
whoami - Displays the current user.
- Example: whoami will display the username of the current user.
tar - Archives and compresses files and directories.
- Example: tar -czf archive.tar.gz directory/ will create a compressed archive called archive.tar.gz from the contents of the directory directory.
grep - Searches for a pattern in a file.
- Example: grep "error" log.txt will search the file log.txt for the pattern "error" and print any lines that match.
head - Displays the first few lines of a file.
- Example: head -n 10 file.txt will display the first 10 lines of file.txt.
tail - Displays the last few lines of a file.
- Example: tail -n 10 file.txt will display the last 10 lines of file.txt.
diff - Compares the differences between two files.
- Example: diff file1.txt file2.txt will compare the contents of file1.txt and file2.txt and print the differences between them.
cmp - Compares the contents of two files byte by byte.
- Example: cmp file1.txt file2.txt will compare the contents of file1.txt and file2.txt byte by byte and report any differences.
comm - Compares the contents of two sorted files line by line.
- Example: comm file1.txt file2.txt will compare the contents of file1.txt and file2.txt, which should both be sorted, and print the lines that are unique to each file.
sort - Sorts the lines of a file.
- Example: sort file.txt will sort the lines of file.txt alphabetically.
export - Exports a shell variable.
- Example: export VARNAME="value" will create a shell variable called VARNAME with the value "value".
zip - Compresses files into a ZIP archive.
- Example: zip archive.zip file1.txt file2.txt will create a ZIP archive called archive.zip containing the files file1.txt and file2.txt.
unzip - Extracts files from a ZIP archive.
- Example: unzip archive.zip will extract the contents of the archive.zip ZIP archive.
ssh - Connects to a remote server using the SSH protocol.
- Example: ssh user@example.com will connect to the server at example.com as the user user.
service - Controls system services.
- Example: service apache2 start will start the Apache web server.
ps - Displays information about running processes.
- Example: ps aux will display a list of all running processes and their resource usage.
kill - Sends a signal to a process to terminate it.
- Example: kill 12345 will send the signal to terminate the process with the process ID 12345.
killall - Terminates all processes with a specified name.
- Example: killall firefox will terminate all processes with the name firefox.
df - Displays information about available disk space on mounted filesystems.
- Example: df -h will display the available disk space in a human-readable format (e.g., in gigabytes or megabytes).
mount - Mounts a filesystem.
- Example: mount /dev/sda1 /mnt/mydisk will mount the partition /dev/sda1 at the mount point /mnt/mydisk.
chmod - Changes the permissions of a file or directory.
- Example: chmod 755 file.txt will give read, write, and execute permissions to the owner and read and execute permissions to everyone else for the file file.txt.
chown - Changes the ownership of a file or directory.
- Example: chown user:group file.txt will change the owner of file.txt to user and the group ownership to group.
ifconfig - Configures network interface parameters.
- Example: ifconfig eth0 up will enable the network interface eth0.
traceroute - Traces the path of packets to a destination.
- Example: traceroute example.com will trace the path of packets from the current system to the destination example.com.
wget - Downloads a file from the internet.
- Example: wget https://example.com/file.zip will download the file file.zip from https://example.com.
ufw - A frontend for managing a firewall.
- Example: ufw allow ssh will allow incoming connections to the SSH service.
iptables - A firewall management tool for Linux.
- Example: iptables -A INPUT -p tcp --dport 80 -j ACCEPT will allow incoming connections to TCP port 80 (the default port for HTTP).
apt - A package manager for Debian-based systems.
- Example: apt update will update the list of available packages.
sudo - Allows a user to run a command with the privileges of the superuser (root).
- Example: sudo apt update will update the list of available packages with root privileges.
cal - Displays a calendar.
- Example: cal will display the current month's calendar.
alias - Creates an alias for a command.
- Example: alias ll='ls -alF' will create an alias ll that runs the command ls -alF.
dd - Copies data from one location to another.
- Example: dd if=/dev/sda of=disk.img will create an image file called disk.img of the contents of the device /dev/sda.
whereis - Shows the locations of a command.
- Example: whereis ls will show the locations of the ls command on the system.
whatis - Shows a short description of a command.
- Example: whatis ls will show a short description of the ls command.
top - Displays information about running processes.
- Example: top will display a list of running processes and their resource usage in real-time.
passwd - Changes the password for a user.
- Example: passwd user1 will prompt you to enter and confirm a new password for the user user1.

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