1. Linux+ Guide to Linux Certification, Second Edition
Chapter 4
Exploring Linux Filesystems

2. Linux+ Guide to Linux Certification, 2e
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
Linux+ Guide to Linux Certification, 2e

3. Objectives (continued)
Display the contents of text files and binary files
Search text files for regular expressions using grep
Identify common text editors used today
Use the vi editor to manipulate text files
Linux+ Guide to Linux Certification, 2e

4. 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
Linux+ Guide to Linux Certification, 2e

5. The Linux Directory Structure (continued)
Figure 4-1: The Windows filesystem structure
Figure 4-2: The Linux filesystem structure
Linux+ Guide to Linux Certification, 2e

6. Linux+ Guide to Linux Certification, 2e
Changing Directories
Home directory: Unique to each user
pwd (print working directory) command: Displays current directory in the directory tree
cd (change directory) command: Change the current directory in the directory tree
~ metacharacter: Refers to home directory
Relative pathname: Pathname of file or directory relative to current directory
Linux+ Guide to Linux Certification, 2e

7. 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
Linux+ Guide to Linux Certification, 2e

8. 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
Linux+ Guide to Linux Certification, 2e

9. Viewing Files and Directories: File Types (continued)
Linked files: Associated with another file
Special device files: Represent system devices
Named pipes: Identify channel that passes information between processes
Socket files: Allow a process on another computer to write to a local file
Linux+ Guide to Linux Certification, 2e

10. Linux+ Guide to Linux Certification, 2e
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
Linux+ Guide to Linux Certification, 2e

11. Filenames (continued)
Table 4-1: Common filename extensions
Linux+ Guide to Linux Certification, 2e

12. Filenames (continued)
Table 4-1 (continued): Common filename extensions
Linux+ Guide to Linux Certification, 2e

13. Linux+ Guide to Linux Certification, 2e
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
Linux+ Guide to Linux Certification, 2e

14. 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
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15. Listing Files (continued)
Table 4-2: Common options to the ls command
Linux+ Guide to Linux Certification, 2e

16. Listing Files (continued)
Table 4-2 (continued): Common options to the ls command
Linux+ Guide to Linux Certification, 2e

17. Wildcard Metacharacters
Wildcard metacharacter: Used to simplify commands specifying multiple filenames
Can be used with most Linux filesystem commands
Linux+ Guide to Linux Certification, 2e

18. Wildcard Metacharacters (continued)
Table 4-3: Wildcard metacharacters
Linux+ Guide to Linux Certification, 2e

19. 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
Linux+ Guide to Linux Certification, 2e

20. 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
Linux+ Guide to Linux Certification, 2e

21. Displaying Content of Text Files (continued)
more and less can be used with output of other commands
If output is too large to fit on terminal screen, use “|” metacharacter
e.g., ls -l | more
Linux+ Guide to Linux Certification, 2e

22. Displaying the Contents of Binary Files
Typically use program that created the file
strings command: Searches for and displays text characters in a binary file
Might indicate purpose of binary file
od command: Displays contents of file in octal format (numeric base 8 format)
Linux+ Guide to Linux Certification, 2e

23. Searching for Text Within Files
Text tools: Search for and manipulate text
Regular expressions (regexp): Text wildcards that assist search for specific text
Match patterns of text
Used by many text tools and programming languages
Including grep, emacs, C++, PERL, and many more
Linux+ Guide to Linux Certification, 2e

24. Linux+ Guide to Linux Certification, 2e
Regular Expressions
Different from wildcard metacharacters
Wildcard metacharacters interpreted by shell; regexps interpreted by text tools
Wildcard metacharacters match characters in filenames; regexps match characters within text files
More regexps than wildcard metacharacters
Common and extended regexps
Linux+ Guide to Linux Certification, 2e

25. Regular Expressions (continued)
Table 4-4: Regular expressions
Linux+ Guide to Linux Certification, 2e

26. Regular Expressions (continued)
Table 4-4 (continued): Regular expressions
Linux+ Guide to Linux Certification, 2e

27. Linux+ Guide to Linux Certification, 2e
The grep Command
grep (global regular expression print) command: Displays lines in a text file matching a given regexp
egrep command: Displays lines of text that match extended regexps
fgrep command: Does not interpret any regular expressions
Returns results much faster than egrep
grep requires two arguments
Text to search for and files to search
Linux+ Guide to Linux Certification, 2e

28. Editing Text Files: The vi Editor
One of the oldest and most popular text editors for UNIX OSs
Vim: Linux equivalent of vi
Standard on most Linux distributions
Advantage is portability, not usability
Used on Unix and Linux
Bi-modal editor (two possible modes):
Command mode: Performs text editing tasks not related to inserting text
Insert mode: Inserts text, but nothing else
User environment is customizable
Linux+ Guide to Linux Certification, 2e

29. Editing Text Files: The vi Editor (continued)
Table 4-5: Common keyboard keys used to change to and from insert mode
Linux+ Guide to Linux Certification, 2e

30. Editing Text Files: The vi Editor (continued)
Table 4-6: Key combinations commonly used in command mode
Linux+ Guide to Linux Certification, 2e

31. Editing Text Files: The vi Editor (continued)
Table 4-6 (continued): Key combinations commonly used in command mode
Linux+ Guide to Linux Certification, 2e

32. Editing Text Files: The vi Editor (continued)
Table 4-6 (continued): Key combinations commonly used in command mode
Linux+ Guide to Linux Certification, 2e

33. Editing Text Files: The vi Editor (continued)
Table 4-7: Key combinations commonly used at the command mode : prompt
Linux+ Guide to Linux Certification, 2e

34. Other Common Text Editors
Mcedit editor (Midnight Commander Editor): Easy-to-use text editor
Supports regexp
Supports use of mouse for highlighting text
Emacs (Editor MACroS) editor: Comparable functionality to vi
Ctrl key combinations to perform special functions
Supports LISP (LISt Processing) artificial intelligence programming language
Linux+ Guide to Linux Certification, 2e

35. Other Common Text Editors (continued)
Table 4-8: Keyboard functions commonly used in the GNU emacs editor
Linux+ Guide to Linux Certification, 2e

36. Other Common Text Editors (continued)
Emacs editor is not easy to use
Must memorize key combinations
Xemacs editor: Version of Emacs for KDE or GNOME GUI environments
Easier to use than emacs
Not available with every distribution
Linux+ Guide to Linux Certification, 2e

37. Other Common Text Editors (continued)
Figure 4-3: The xemacs text editor
Linux+ Guide to Linux Certification, 2e

38. Other Common Text Editors (continued)
Graphical text editors available with most Linux distributions:
nedit editor
gedit editor: Distributed with GNOME environment
kedit editor: Distributed with KDE environment
gedit and kedit offer more functionality than nedit
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39. Other Common Text Editors (continued)
Figure 4-4: The nedit text editor
Linux+ Guide to Linux Certification, 2e

40. Other Common Text Editors (continued)
Figure 4-5: The gedit text editor
Linux+ Guide to Linux Certification, 2e

41. Other Common Text Editors (continued)
Figure 4-6: The kedit text editor
Linux+ Guide to Linux Certification, 2e