4-Browsing Folders and Intro to File Permissions
- ls
    - ls
        - show the content of the current directory
    - ls /filepath
        - show the content of the specified directory
    - ls -l
        - detailed list
        - Columns:
            - File Permissions
            - Links to a file
            - Owner
            - Group
            - # of Bytes
            - Modified Date
            - File Name
    - ls -lh
        - show the # of bytes in Human readable format
            - #b=bytes
            - #k=kilobytes
            - #m=megabytes
            - #g=gigabytes
- UNIX File Permissions
    - 3 Levels of Permissions
        - 1. User Level
            - Each file only has 1 owner
        - 2. Group Level
            - Each file has only 1 group
        - 3. Everyone Else
    - 3 Types of Permissions
        - 1. Read Access
        - 2. Write Access
        - 3. Execute Access
    - 10 or 11 character string
        - -rwxrwxrwx
        - 1st Character
            - - = file
            - d = directory/folder
            - l = symbolic link/alias
            - other characters possible,  but rare
        - next 9
            - Seen in groups of 3
                - First 3: User Permissions
                - Next 3: Group Permissions
                - Final 3: Everyone Permissions
            - If the permission is given, the letter applying to that
              permission is shown
            - if not, then a -
            - example: drwxrw-r--
            - Read and Write access are self explanatory
                - execute:
                    - for a file: run/execute that file
                    - for a directory: list the contents of the
                      directory
        - When you access a file, UNIX checks to see who you are, and
          what groups you belong to, and compares it to the file
            - If you are the owner, it applies the owner permissions
                - drwx------
            - If not, it checks if you belong to the group which owns
              the file, if so, it applies group permissions
                - d---rwx---
            - If not, the everyone else permissions are applied
                - d------rwx
    - Final Character
        - Not always there
        - 2 Possibilities
            - +
                - extended security permissions
                    - rare, mostly on system files
            - @
                - extended attributes
                    - more common
                    - color, icon, spotlight comments, etc
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