Exploring interfaces and filesystems

1. Exploring interfaces and filesystems Unit objectives • Outline structure of the Linux interface, and roles of the kernel, terminal and shell • Enter shell commands, find documentation, use metacharacters, shut down system • Learn directory structure, file types, and use wildcards • Display contents of text and binary files • Search text files by using grep, identify common text editors, and use the vi editor

2. Topic A • Topic A: Linux interfaces • Topic B: Basic shell commands • Topic C: Files and directories • Topic D: Displaying the contents of files • Topic E: Searching and editing text files

3. Shells, terminals, and the kernel • Kernel • The core component of the OS • Terminal • Screen that allows you to log in • Shell • Runs within the terminal • Interface that accepts commands and passes them to the kernel • BASH Shell (Bourne Again Shell): the default shell continued

4. Shells, terminals, and the kernel, continued

5. A GNOME terminal

6. A KDE terminal

7. Exercise A-1 Discussing terminals and shells

8. Topic B • Topic A: Linux interfaces • Topic B: Basic shell commands • Topic C: Files and directories • Topic D: Displaying the contents of files • Topic E: Searching and editing text files

9. Basic Shell Commands • Commands • Indicate name of the program to execute • Options • Letters starting with a dash “-” that alter way the command works • Arguments • Specify the parameters the command works upon

10. Some common Linux commands

11. Shell metacharacters • Key combinations that have special meaning in the Linux OS • One of the most commonly used metacharacters is the $ character

12. Common BASH shell metacharacters

13. Activity B-1 Using shell commands and metacharacters

14. Getting command help • Manual pages • Commonly referred to as man pages • Documents the command’s function and the syntax it accepts

15. Manual page section numbers

16. Activity B-2 Getting help

17. Activity B-3 Shutting down the system

18. Topic C • Topic A: Linux interfaces • Topic B: Basic shell commands • Topic C: Files and directories • Topic D: Displaying the contents of files • Topic E: Searching and editing text files

19. The Linux directory structure

20. The Linux directory structure • Directory • Special file used to organize other files into a logical structure • Absolute pathname • Full pathname to a certain file or directory starting from the root directory

21. Home directory • Home directory • A directory for users to store personal files and information • Each user has a sub-directory

22. Changing directories • pwd (print working directory) • Used to identify the current directory path • cd (change directory) • Used to move from one directory to another

23. The ~ metacharacter and relative paths • ~ • Refers to the current user’s home directory • Can specify another user’s home directory by adding the username after ~ • Relative pathname • Pathname of a target directory relative to your current location in the tree

24. Tab-completion • Tab-completion • Fills in the remaining characters of a unique filename or directory name when you press the Tab key

25. Activity C-1 Logging on and navigating the file structure

26. File types • Text files • Binary data files • Executable program files • Directory files • Linked files • Special device files • Named pipes and socket files

27. Filenames • Filename • User-friendly identifier given to a file • Filename suffixes • Identifiers following a dot (.) at the end of a filename • used to denote the type of the file

28. Filename extensions

29. The ls command • Used to list the files in a directory • Most common method for displaying files • Displays all the files in the current directory • You can use an argument with ls to list a directory different from current one

30. Ls –F file type characters • @ Linked file • * Executable file • / Subdirectory • = Socket file • | Named pipe

31. The file command • File command • Displays detailed information about any file • Works with multiple files • Uses * to include all files in a directory

32. Hidden files • Hidden files • Files that are not normally displayed with common filesystem commands • represent important configuration files or program directories

33. ls command options continued

34. ls command options, continued

35. Activity C-2 Examining files and file types

36. Wildcard metacharacters • Can simplify more than one filename to a command • Interpreted by the shell and can be used with most filesystem commands • Matches certain portions of filenames or an entire filename continued

37. Wildcard metacharacters, continued

38. Activity A-3 Using wildcard metacharacters

39. Topic D • Topic A: Linux interfaces • Topic B: Basic shell commands • Topic C: Files and directories • Topic D: Displaying the contents of files • Topic E: Searching and editing text files

40. Displaying content of text files • cat command • Display the entire contents of a text file to the screen • tac command • Displays a file to the screen beginning with the last line of the file and ending with the first line of the file • head command • Displays the first 10 lines (including blank lines) of a text file to the terminal screen • Can also take a numeric option specifying a different number of lines to display continued

41. Displaying content of text files, continued • tail command • By default, displays the last 10 lines (including blank lines) of a text file to the terminal screen • Can also take a numeric option specifying a different number of lines to display

42. Other text file viewing commands • more command • Displays a text file page-by-page and line-by-line • Gets its name from the pg command once used on UNIX system • less command • Displays a text file page-by-page • Use the cursor keys to navigate the file

43. Activity D-1 Displaying text file contents

44. Displaying the contents of binary files • strings commands • Linux command used to search for and display text characters in a binary file • od command • Linux command that is used to display the contents of a file in octal format (numeric base 8 format) • Safe to use on binary files and text files

45. Activity D-2 Displaying binary data

46. Topic E • Topic A: Linux interfaces • Topic B: Basic shell commands • Topic C: Files and directories • Topic D: Displaying the contents of files • Topic E: Searching and editing text files

47. Searching for text within files • Regular expressions (regexp) • Special metacharacters used to match patterns of text within text files • Commonly used by many text tool commands such as grep

48. Regular expressions and wildcards • Regular expressions are interpreted by a text tool program, wildcard metacharacters are interpreted by the shell, • Regular expressions match characters within text files, wildcard metacharacters match characters in filenames or directory names continued

49. Regular expressions and wildcards, continued • Wildcard metacharacters regular expressions usually have different definitions than wildcard metacharacters • More metacharacters are available for regular expressions • Regular expressions are divided into two different categories: • Common • extended continued

50. Regular expressions