Linux Commands Basic for beginners

 

Linux commands are essential for interacting with the operating system via the terminal. Below is a concise overview of basic Linux commands, their purposes, and examples to help you get started.

Key Concepts

• Linux commands are case-sensitive and typically entered in lowercase.
• Commands are often combined with options (flags) and arguments.
• Use man <command> (e.g., man ls) to access the manual for any command.

Basic Linux Commands and Examples

1. Navigating the File System
• pwd: Prints the current working directory.
  • Example: pwd
    • Output: /home/user
• ls: Lists files and directories in the current directory.
  • Example: ls -l
    • Output: Detailed list with permissions, owner, size, etc. (e.g., drwxr-xr-x 2 user user 4096 May 23 15:30 documents)
• cd: Changes the current directory.
• Example: cd /home/user/documents
  • Moves to the documents directory.
• Example: cd ..
• Moves up one directory level.

1. File and Directory Management
• mkdir: Creates a new directory.
  • Example: mkdir my_folder
    • Creates a directory named my_folder.
• rm: Removes files or directories.
  • Example: rm file.txt
    • Deletes file.txt.
  • Example: rm -r my_folder
    • Deletes my_folder and its contents recursively.
• cp: Copies files or directories.
  • Example: cp file.txt /home/user/backup/
    • Copies file.txt to the backup directory.
• mv: Moves or renames files/directories.
• Example: mv file.txt newfile.txt
  • Renames file.txt to newfile.txt.
• Example: mv file.txt /home/user/documents/
• Moves file.txt to the documents directory.

1. Viewing and Editing Files
• cat: Displays file contents.
  • Example: cat file.txt
    • Outputs the contents of file.txt.
• less: Views file contents interactively (scrollable).
  • Example: less file.txt
    • Opens file.txt for viewing; press q to quit.
• nano: Simple text editor.
  • Example: nano file.txt
    • Opens file.txt for editing; save with Ctrl+O, exit with Ctrl+X.
• touch: Creates an empty file or updates a file’s timestamp.
• Example: touch newfile.txt
• Creates an empty file named newfile.txt

1. File Permissions
   • chmod: Changes file permissions.
     • Example: chmod 755 script.sh
       • Grants owner full permissions (read, write, execute) and others read/execute permissions.
   • chown: Changes file ownership.
     • Example: chown user:group file.txt
       • Changes the owner of file.txt to user and group to group.
2. System Information
   • whoami: Displays the current user.
     • Example: whoami
       • Output: user
   • df: Shows disk space usage.
     • Example: df -h
       • Output: Disk usage in human-readable format (e.g., GB).
   • top: Displays real-time system processes.
     • Example: top
       • Shows running processes; press q to quit.
   • uname: Displays system information.
     • Example: uname -a
       • Output: Kernel and system details.
3. File Searching and Filtering
   • find: Searches for files/directories.
     • Example: find /home -name "*.txt"
       • Finds all .txt files in /home.
   • grep: Searches text within files.
     • Example: grep "error" log.txt
       • Finds lines containing “error” in log.txt.
   • wc: Counts lines, words, or characters.
     • Example: wc -l file.txt
       • Output: Number of lines in file.txt.
4. Process Management
   • ps: Lists running processes.
     • Example: ps aux
       • Shows all processes with details.
   • kill: Terminates a process by ID.
     • Example: kill 1234
       • Stops the process with PID 1234.
   • killall: Terminates processes by name.
     • Example: killall firefox
       • Stops all Firefox processes.
5. Networking
   • ping: Checks connectivity to a host.
     • Example: ping google.com
       • Tests connection to google.com.
   • curl: Transfers data from/to a server.
     • Example: curl https://example.com
       • Downloads content from example.com.
   • wget: Downloads files from the web.
     • Example: wget https://example.com/file.txt
       • Downloads file.txt.
6. Piping and Redirection
   • | (pipe): Sends output of one command as input to another.
     • Example: ls -l | grep txt
       • Lists files and filters for those containing “txt”.
   • >: Redirects output to a file (overwrites).
     • Example: echo "Hello" > file.txt
       • Writes “Hello” to file.txt.
   • >>: Appends output to a file.
     • Example: echo "World" >> file.txt
       • Appends “World” to file.txt.

Tips for Beginners

• Combine Commands: Use pipes (|) to chain commands, e.g., cat file.txt | grep "pattern".
• Use Tab Completion: Press Tab to auto-complete commands or file names.
• Learn Shortcuts: Ctrl+C stops a command, Ctrl+D exits a shell.
• Practice Safely: Be cautious with rm -rf, as it deletes files permanently.