Linux Command Suumary
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This document provides an overview of the Linux operating system and commands. It begins with course objectives to introduce Unix concepts, commands, and the VI editor. It then discusses what an operating system is and why they are needed before exploring the evolution, flavors, and architecture of Unix/Linux. Key topics covered include the file system structure, absolute vs relative paths, how Unix sessions work, login sequences, command syntax, and standard input/output/error. The document also examines regular expressions, shell metacharacters, editors like VI, and permissions.
![Unix Command Structure
Unix Command line structure
command [options] [arguments]
Refer the following word Doc for Detail Command](https://image.slidesharecdn.com/linuxpart1-130503175815-phpapp02/85/Linux-Command-Suumary-15-320.jpg)
![Regular Expressions
What is it?
String of ordinary and metacharacter which can be used to
match more than one type of pattern.
Uses character set
* , [], ^, $, {}, etc.](https://image.slidesharecdn.com/linuxpart1-130503175815-phpapp02/85/Linux-Command-Suumary-18-320.jpg)
![The Shell Metacharacters.
See Demo at
/home/oresoft/Training/Linux/commands/shellChar
* - Matches all filenames in current directory.
? - Matches a single character.
[abc] - Matches a single character – either a, b or c.
[!abc] - Matches a single character – which is not a, b or c.
[a-c] – Matches a single character which is within the range of a and c.
^abc – Matches the pattern abc at the beginning of the line.
abc$ - Matches the pattern abc at the end of the line.](https://image.slidesharecdn.com/linuxpart1-130503175815-phpapp02/85/Linux-Command-Suumary-19-320.jpg)
![Vi editor commands
To move around
h, j, k, l, ^D, ^U, G, 0, ^, $, w, b
Inserting/Deleting text
i, a, I, A, r, R, o, O, dd, dw, c$, D, x, X.
Changing/Replacing text.
cc, cw, c$, ~, J, u, . , yy, yw, p, P
File manipulation.
:w, :wq, ZZ, :w!, :q, :q! , :![command]](https://image.slidesharecdn.com/linuxpart1-130503175815-phpapp02/85/Linux-Command-Suumary-25-320.jpg)
![Examples of chmod
Syntax.
chmod [0-7][0-7][0-7] filename (Absolute
Mode)
chmod [ugo][+-][rwx] filename (Symbolic
Mode)
$ chmod a=rw temp
$ ls -l temp-rw-rw-rw- 1 alex pubs 57 Jul 12 16:47 temp](https://image.slidesharecdn.com/linuxpart1-130503175815-phpapp02/85/Linux-Command-Suumary-34-320.jpg)
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Linux Command Suumary
- 2. Course Objective To introduce the Unix Operating System Concept. To introduce standard Unix commands. To introduce VI editor.
- 3. References Text Book Reference Brain W. Kernighan and Rob Pike, The UNIX Programming Environment. A Practical Guide to Linux® Commands, Editors, and Shell Programming - Mark Sobell's Web Reference Unix Tutorial For Beginners Introduction to Unix http://www.cis.uab.edu/cs344/spring2005/
- 4. What is Unix Operating System Unix OS is a Program Unix OS provides interface between users and bare hardware Unix OS manages resources: CPU(s), memory, disks, other I/O devices. Operating System users
- 5. Why do we need Operating System ? To Interact with Computer Hardware End User Computer Hardware Operating-System Utilities Application Programs OS Designer System Programmer Application Programmer E.g. compiler, librari es, shell E.g. database, web servers
- 6. Evolution of Unix OS
- 7. Flavors of Unix AIX (Advanced IBM Unix) HP-UX ( Hewlett Packard Unix) BSD ( Berkeley Software Distribution. ) SCO UNIX SOLARIS LINUX, etc
- 9. System Architecture Major components of Unix are : Kernel Monitors and controls hardware resources Allocates them among its users in an optimal manner Utilities Programming tools that do standard tasks extremely well. EX: cp, grep, awk, sed, bc, wc, more Shell Command Line Interpreter. Provides a processing environment for the user programs. User Applications Programs written by the user
- 10. Processing Environment • User Program – Set of instructions written by the user • Process – Instance of a program under execution • Shell – Provides a processing environment for the user programs
- 11. Structure of Unix File System
- 12. Absolute Path and Relative Path The Absolute Path The entire pathname starting from root(/) Example /home/oresoft/. The Relative Path The path relative to your present working directory Example cd ..
- 13. How Unix Session Works. USER TYPES COMMAND SHELL EXECUTES UTILITY TO CARRY OUT COMMAND SHELLASKS FOR A COMMAND USER INTERACTS WITH UTILITY SHELL PROMPTS FOR NEXT COMMAND USER TYPES CONTROL-D LOGOUT LOGIN
- 14. Login Sequence. /etc/passwd 1 /etc/shadow 2 /etc/group 3 /etc/profile 4 /etc/profile.d/*.sh 5 ~/.bash_profile 6 ~/.bashrc 7 /etc/bashrc 8
- 15. Unix Command Structure Unix Command line structure command [options] [arguments] Refer the following word Doc for Detail Command
- 16. Concept of stdin, stdout and stderr Operating System Another Computer program running stdout stderr stdin Keyboard A Computer program running stdout stderr stdin Monitor
- 17. Standard Files Standard Input (0) This file is opened by shell to accept information. Standard Output (1) This file is opened by shell to direct output Standard Error (2) This file is opened by shell for writing error messages
- 18. Regular Expressions What is it? String of ordinary and metacharacter which can be used to match more than one type of pattern. Uses character set * , [], ^, $, {}, etc.
- 19. The Shell Metacharacters. See Demo at /home/oresoft/Training/Linux/commands/shellChar * - Matches all filenames in current directory. ? - Matches a single character. [abc] - Matches a single character – either a, b or c. [!abc] - Matches a single character – which is not a, b or c. [a-c] – Matches a single character which is within the range of a and c. ^abc – Matches the pattern abc at the beginning of the line. abc$ - Matches the pattern abc at the end of the line.
- 20. Editor in Unix Need for editor in Unix Types of editor Line Editor ed : UC Berkeley ex : Powerful than ed, Bell Systems Full Screen Editor vi (stands for visual) vim – vi improved emacs (GNU)
- 21. The vi Editor. The important characteristic features are: Omnipresent Works on different Unix flavors Fast Various operations are very fast Powerful UNDO features Text in lines could be undone with very less effort
- 22. The vi Editor. The limitations are: Less user-friendly No graphical user interface Highly Case-sensitive Letter in small case has a different implementation in comparison with the same letter in upper case Keystrokes could have more than one meaning A letter (of the same case) has different implementation across different modes.
- 23. The vi Editor. Modes of working: Command Mode Keys are interpreted as commands Insert Mode Keys are interpreted as data Escape Mode Keys are interpreted for saving/exiting purposes
- 24. vi Operating modes. Command mode Insert mode i, I , o, O, a, A .. esc Last line mode Enter: :q
- 25. Vi editor commands To move around h, j, k, l, ^D, ^U, G, 0, ^, $, w, b Inserting/Deleting text i, a, I, A, r, R, o, O, dd, dw, c$, D, x, X. Changing/Replacing text. cc, cw, c$, ~, J, u, . , yy, yw, p, P File manipulation. :w, :wq, ZZ, :w!, :q, :q! , :![command]
- 26. Searching a pattern /pattern Searches forward for first occurrence of a pattern. ?pattern Searches backward for first occurrence of a pattern. n Repeats the last search. N Repeats the last search command in opposite direction.
- 27. Pattern Substitution. :s/ptn1/ptn2 Replaces first occurrence of ptn1 with ptn2. : s/ptn1/ptn2/g Replaces all occurrences in the current line. : m, n s/ptn1/ptn2/g Replaces all occurrences in lines m to n. : ., $ s/ptn1/ptn2/g Replaces all occurrences from current line to end of file.
- 28. Customizing vi. The set command :set all :set nu The abbr command :abbr itl ―Infosys Technologies Ltd‖ The map command :map ^X :wq
- 29. System Variables. PATH Search path referred by Unix for any command. echo $PATH HOME Indicates the home directory for the user. echo $HOME
- 30. set command Used for display all the environment variables. Shows the current values of system variables. Also allows conversion of arguments into positional parameters. Syntax : set set command.
- 31. File Permission - Absolute Mode. r w x r w x r w x 4 2 1 4 2 1 4 2 1 Owner Group Other Group OthersOwner rwxrwxrwx Permission Value R 4 W 2 x 1 - No Permission
- 32. Summary Background Features of Unix Unix System Architecture Unix File System General Unix commands and utilities Processes Regular Expressions Vi Editor Modes of operation
- 33. File Permission – Symbolic Mode. Who User Class Meaning U User Owner of file G Group Group to which owner belongs O Other All other Users Who Meaning r Sets read permission w Sets write permission x Sets exec permission Symbolic mode user class specification Symbolic mode permissions
- 34. Examples of chmod Syntax. chmod [0-7][0-7][0-7] filename (Absolute Mode) chmod [ugo][+-][rwx] filename (Symbolic Mode) $ chmod a=rw temp $ ls -l temp-rw-rw-rw- 1 alex pubs 57 Jul 12 16:47 temp
- 35. Unmasking File Permission umask Stands for user creation mask. Sets default permissions for a newly created file and directory. The value can be changed. Example 6 6 6 - System wide default permissions - 0 2 2 - Denial ‗mask‘ set by UMASK 6 4 4 - Resultant permissions that will be set on all files created (-rw-r—r--)