UNIX Basics

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Main functions of Kernal

- Manages task and storage - Creates processes - Controls processes - Manages memory - Manages files systems - Manages communications - Enforces security

Industries in which UNIX based systems can be found

- Network management - TCP/IP - Telco - Internet - Banking - Shipping - Security - Military - Factory automation - macOS - iOS - Android

Main functions of Utilities

- Some process management - User management (passwd) - Printing (lp) - Program development toos

What makes UNIX unique?

-Multi-tasking capability - Multi-user capability - Portability (can move from one computer to another with minimum code changes) - UNIX tools (tools for program development) - Library of application software - VERY ROBUST (reliability & scalability)

UNIX Manual Sections

1. General User Commands 2. System Calls 3. User level library functions 4. File formats 5. Standards, Environments and Macros 6. Games 7. Device and Network Interfaces

IP Address

196.1.174.205

What year was UNIX founded?

1969 - Started in 1965 at Bell Labs and General Electric

How many splits are there in UNIX development?

2 (1977-78) - BSD (Berkeley Software Distribution) - 1977 - System V

What happened in June 1974?

5th edition of UNIX released

How to Change Password

passwd Comp112561

Inode

Index node that stores all the information about a regular file or directory

init

Initialises the system and then starts other processes to set up standard input, standard output, and standard error

Kernel

Innermost level - Actual operating system (single large program that always resides in memory) - "Kernal is IN UNIX"

Commands

Instructions you give the system to tell it what to do

Main functions of Shell

Interprets commands: - Reading input and parsing the command line - Evaluating special characters - Setting up pipes, redirection, and background processing - Handling signals - Setting up programs for execution - Presents the users with a prompt.

Abstractions

Isolates the application programmers and users from the details of underlying hardware

First Layer

Kernal

Main Components of UNIX

Kernel, Shell, Utilities

File Systems

Method for storing and organising computer files and the data they contain to make it easy to find and access them

What is UNIX?

Multi-tasking, multi-user operating system (OS)

What does Multics stand for?

Multiplexed Information and Computing Service -Mainframe timesharing system

What version of UNIX do we use today?

SYSV version 11 enviornemnt

Three Main Features of UNIX

Safe, efficient, abstract

Job

Sequence of instructions given to the computer from the time you initiate a particular task

Utilities

Small or large program which offers lots of flexibilities - UNIX commands are standardised programs

Shell

Special program used as an interface between the user and the kernal - It is a command interpreter - Responsible for setting up user's enviornment

Third Layer

The Shell

UNIX Philosophy

"Small is beautiful" ~ Make each program do one thing well - A hierarchical file system - Pipes - Shell scripts to increase leverage and portability - Allow user to tailor enviornment

How much is the UNIX industry worth?

$74 Billion

1973 Forth Edition:

(1973) Rewrote the OS in the C programming language - Became worlds first PORTABLE OS - Changed history of OSs

Three major shells

- Bourne Shell - C Shell - Korn Shell

UNIX Rules

- Case-sensitive - Commands can only be entered at the shell prompt - Command lines must end with "return" - Options often begin with "-" - More than one option can be included with many commands

6 Basic elements of UNIX

- Commands - Files - Directories - Environment - Processes - Jobs

Hard Link Limitations

- Do not span across file systems - Do not allow links to directories

Popular flavours of UNIX

- Fundamental design - Commands and features - Hardware platforms (processors) - Proprietary software (commercial) or free software

UNIX Filenames

- Little restrictions on filenames - Up to 256 characters long - Cannot have "/" - Use "_" - Case-sensitive - Use extensions for ease (.txt)

1982 System III

AT&T's UNIX System Group (USG) release System III - First public release outside of Bell Labs

Safe

Access to a printer by allowing only one application program to send data directly to the printer at any one time

Second Layer

All applications and commands in UNIX

What is the first programming language UNIX was written in?

Assembly language, AND WAS FIRST RAN ON A PDP-7, then in 1970 ran of PDP-11

What language is UNIX currently written?

C

Environment

Collection of items that describe or modify how your computing session operates

Files

Collections of data that have been given filenames - Stored in directories

Process

Command or application running on computer

Directory

Contains many files, as well as other directories

Initial goals for UNIX

Convenient, interactive, OS that could support many users

Two people who created UNIX

Dennis Richie and Ken Thompson

Open Systems

Developed in 1980s by group of UNIX vendors - Were those that would meet agreed specifications or standards to reduce the cost of porting software

1983 System V

First supported release

1975 Sixth Edition

First version to be available outside of Bell Labs

1971 First Edition:

Had assembler (written in assembler language) for a PDP-11 - Used for text processing of documents, letters, technical documents etc.

026

Typical umask setting

What UNICS stand for?

Uniplexed Information and Computing System?

Efficient

Use of the CPU by suspending programs that are waiting for I/O operations to complete, to make way for programs that can use the CPU more productively

Final Layer

User

UNIX Syntax

command [-flag options] file/expression - ec -1 file1

What shell are you in (command)?

echo $SHELL OR grep Comp112561 /etc/passwd


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