Exploring Linux File Systems - Unix Systems - Lecture Slides, Slides of Advanced Operating Systems

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Chapter 4

Exploring Linux File systems

Objectives

• Understand and navigate the Linux directory structure using relative and absolute pathnames
• Describe the various types of Linux files
• View filenames and file types
• Use shell wildcards to specify multiple filenames

The Linux Directory Structure

• Directory: Used to organize other files into a logical tree structure
• Absolute pathname: Pathname from the root directory to a certain file or directory
• Root: The top level directory
  • referred to using the / character

The Linux Directory Structure

(continued)

Figure 4-1: The Windows filesystem structure

Figure 4-2: The Linux filesystem structure

Changing Directories (continued)

• Subdirectory: Directory residing within another directory
• Tab-completion: Pressing the Tab key fills in remaining characters of a unique filename or directory name - BASH shell feature

Viewing Files and Directories: File Types

• Text files: Store information in a readable text format
• Binary data files: Store information associated with executable programs
• Executable program files
• Directory files

Filenames

• Filename: Identifier given to a file
• Filename extensions: Identifiers following a dot (.) at end of filename - Denote file type - Most files on Linux do not have file extensions

Filenames (continued)

Table 4-1: Common filename extensions

Listing Files

• ls command: List the files in a directory
  • May pass an argument indicating the directory to be listed - – F switch: Argument to list file types - – l switch: Argument to list long file listings
• Alias: Shortcut for a command
• ll command: Alias for ls -l
• File command: Displays file type of any file

Listing Files (continued)

• Hidden files: Files not normally displayed to user - Filenames start with a dot (.) - Configuration files often hidden - ls – a command: Displays hidden files

Listing Files (continued)

Table 4-2 (continued): Common options to the ls command

Wildcard Metacharacters

• Wildcard metacharacter: Used to simplify commands specifying multiple filenames - Can be used with most Linux filesystem commands

Displaying Content of Text Files

• Concatenation: Joining text together
• cat command: Displays (concatenates) contents of a text file to the screen - -n switch: Displays line number and contents
• Log files: Contain records of past system events - New events appended to end
• tac command: Displays files in reverse order
• head command: View first few lines of a file

Displaying Content of Text Files (continued)

• tail command: View last few lines of a file
  • Can also specify what line number to start at
• more command: Displays text files page-by- page - Space key goes to next page - Enter key goes to next line
• less command: Same as more command, but can also use cursor to scroll