chapter 1-5 summary slides - university of...

Outline

Chapter 1-5 Summary Slides

Cam Macdonell

Dept of Computing ScienceUniversity of Alberta

September 8th, 2005

Cam Macdonell Chapter 1-5 Summary Slides

OutlineChapters 1-3Chapters 4-5

Getting Started with Unix

1 Unix and LinuxUnixLinux, BSD, Mac OS X

2 Introduction to ShellsAn Overview of ShellsAdjusting to ShellsBash and TcshLogging In

3 Using the Command LineBasic CommandsManaging FilesOther Commands

OutlineChapters 1-3Chapters 4-5

Getting Started with Unix

4 File SystemsFile SystemsFilesWorking Directory

5 More on ShellsRunning a ProgramManuals and OptionsUseful Shell TipsSummary

Chapter 1 - The (Brief) History of Unix and Linux

Part I

History of Unix and Linux

Chapter 1 - The (Brief) History of Unix and LinuxUnixLinux, BSD, Mac OS X

The History of Unix

Unix was designed by Ken Thompson and Dennis Ritchie inthe ’70s at Bell Labs

It is a multi-user operating system that allows several peopleto use the computer at once

Since then many Unix-compatible OSes have been written

The History of Unix

Unix popularity is growing

In the past Unix-like OSes predominantly used for servers

There are now several Unices in everyday desktop use

Linux and Mac OS X are the most common

Popular in Universities and research institutions

Most Unices are available for free in some way

They are also open-source

Chapter 2 - Getting Started

Part II

Shells

What Are Shells?More about ShellsTypes of ShellsLogging In To A Computer

Shells are very useful

Shells are a command-line interface (i.e. typing)

Used before GUIs were developed

Still used for speed (faster than GUIs) and functionality

there is a great deal more to shells that make them veryflexible and powerful

Shells take time to learn

Can seem cryptic at the start

Require memorization of basic commands

ls,cd,mv,rm,man,info,find,gcc

Once you become comfortable you will prefer them for sometasks

Can be the source of comp sci ”holy wars”!

Bash and Tcsh

The two most common shells are:

BASH: Bourne Again SHell

TCSH: Tenex C SHell

There are many more - zsh,ksh,...

Even Microsoft has a new shell for Windows Vista namedMonad

Bash and Tcsh

TCSH: Tenex C SHell

Bash and Tcsh

TCSH: Tenex C SHell

Bash and Tcsh

TCSH: Tenex C SHell

Bash and Tcsh

TCSH: Tenex C SHell

How to log in to a machine

You can use a shell by opening a terminal program

In a networked environment computers are named

You log in to a machine in 2 ways

Sitting in front of itssh to it

To ssh, you must know the computer’s name

Logging In cont...

What’s your computer’s name?

Run the commanduname -a

To log in type ssh <machine name here>

Try logging in...

to ohaton.cs.ualberta.cato your neighbour’s machine (ask for the name)

See who’s logged in to your machine

run the command who

Logging In cont...

Try logging in...

run the command who

Logging In cont...

Try logging in...

run the command who

Logging In cont...

Try logging in...

run the command who

Logging In cont...

Try logging in...

run the command who

Chapter 3 - Command Line Utilities

Part III

Command Line Utilities

Chapter 3 - Command Line UtilitiesBasic CommandsManaging FilesOther Commands

Common Utilities

Chapter 3 summarizes the most common utilities (pg. 70)

We will try out some of the most important...

Common Utilities

Chapter 3 summarizes the most common utilities (pg. 70)

We will try out some of the most important...

Listing, Viewing, Copying Files

list the files in a directory - ls

display a text file - cat

copy a file - cp

delete a file - rm (remove)

copy a file - cp

Let’s try it

create a simple file$ echo this is a simple file > simple

display the contents$ cat simple

tab completiontry typing ’cat sim’ and hitting the tab key

list the file$ ls

create a copy$ cp simple simple.copy

list again (with more information)$ ls -l

Let’s try it

list the file$ ls

Let’s try it

list the file$ ls

Let’s try it

list the file$ ls

Let’s try it

list the file$ ls

Let’s try it

list the file$ ls

Let’s try it

list the file$ ls

Add directories to the mix

create a directory$ mkdir simple

oops! That name is already being used$ mkdir backups

move our copy in to the new directory$ mv simple.copy backups

move in to directory$ cd backups

list$ ls -l

move back to the original directory$ cd .. (.. is a reference to one directory above)

list$ ls -l

There are thousands of commands

We have only scratched the surface

It will take time to learn

There are also lots of options for every command

like the ’-l’ option we saw for ls

The text book is a great reference

Some other very important commands are:gcc,grep,lpr,gdb,less,man

diff,tar,bzip2,find

The more you use a command line, the more comfortable youwill become

diff,tar,bzip2,find

Chapter 4 - The Linux File System

Part IV

The Linux File System

Chapter 4 - The Linux File SystemFile SystemsFilesWorking Directory

What Are File Systems

File systems organize data on hard disks

Hard disks are high volume, persistent and slow

Without being able to store data computers would not be veryuseful

You will have your own home directory in which you storeseveral GBs of data that can only be accessed by you fromany CS computer

Hierarchies

All modern file systems are hierarchical

Folders contain files and more folders (Fig 4-3)

The top or root of the file system

In Windows, it’s the drive name C: (but you can have severaldrives)In Unix, the / directory (called ’root’) is top

Your home directory is not at the root, it is several directoriesbelow

Hierarchies

Filenames

Every file has a name and may or may not have an extension

Some common extensions

compute.c - a C source filecompute.o - an object code fileassn1.tar.gz - an compressed archive filereport.pdf - a PDF file

Extensions are not always necessary in Unix, but can behelpful to know what a file is used for

Filenames

The Working Directory

With a command line, you are always working in a particulardirectory called the current working directory

To see what it is, run the command: pwd - try it!

The hierarchy can cause some confusion

ls tmp - list the contents of tmp under the working directoryls /tmp - list the contents of tmp under the root directoryWARNING: one little slash ’/’ at the start of a filename makea lot of difference

Other important characters

a single dot (.) refers to the current directory - try ls .a double dot (..) refers to the directory up the hierarchy - tryls ..

Managing Directories

You can make as many directories as you like

mkdir is the command to make a directory

rmdir is the command to delete a directory

But, the directory must be empty before it can be removed

ls lists the contents of a directory

by default, it lists the working directory - ls and ls . do thesame thingBut, you can provide a directory name

ls simple

ls mydir

ls simple

ls mydir

ls simple

ls mydir

ls simple

ls mydir

ls simple

ls mydir

Chapter 5 - The Shell

Part V

Shells

Running a ProgramManuals and OptionsUseful Shell TipsSummary

Running a program

A shell is used to run programs and perform tasks

Our notation is to use a dollar sign ($) as the prompt

Typically your prompt will look like this[cam@ug01 ]$

To run a program, you type its name and any arguments thatgo with it

The first word on a line is the program, everything after is anoption or an argument

examples

$ ls -l ..$ gcc compute.c$ grep -i int compute.c

Running a program

examples

Running a program

examples

Running a program

examples

Running a program

examples

Manuals and Options

Some programs have hundreds of options

They are used to give a program flexibility and differentbehaviours

Check out the options for ls (or any program) by looking inits manual

type man and the program name to see that program’s manualtry man lstry man catand yes even man man

Manual pages are great resources, make using them a habit

Manuals and Options

The Wild Card *

What if you want to remove all the files in a directory?

Do you have to list them all manually?

You can use the wild card character *

The * will match any string characters

try ls t* - list all file that begin with a ’t’try rm a*c - remove all files that begin with ’a’ and end in ’c’Don’t try this: rm * - this will remove all files in the currentdirectoryBE CAREFUL when removing files! - there’s no recycle bin inshellsQuestion: What files will ls c*.*t list?

The wild card will work with any command line program, itspart of the shell, not a particular program like ls or rm

The Wild Card *

Re-Direction

Some programs like ls and cat display output

You can capture this output for use with other programs

It’s called re-direction

Re-Direction

Re-Direction to and from file

Let’s try redirecting output from a program to a file

$ ls -l > ls.out$ cat ls.out$ who > who.out

Careful! Redirecting can overwrite the file if it already exists

Let’s try redirecting data from a file into a program

$ cat < who.out

Re-Direction to another program

grep is useful program that finds strings that match a searchstring

Let’s try redirecting output to the grep program

ps aux lists all the programs running on a computers - there’slots!

But what if we only want to know how many bash shells arerunning

We’ll get grep to pick out the lines that have the word ’bash’in them

$ ls -l grep bash

The pipe — sends data out of one program into another

Read about standard input and standard output on pp.115-123

$ ls -l grep bash

Summary

Shells are very powerful and complex tools for working with acomputer

They can take time to master and there’s always more to learn

Remember to play around with them and try different things

No matter how much you use them, you will always belearning new ways that shells can help you to work moreefficiently

...and defending your shell to the death versus others!

your allegiance to your shell will only be eclipsed by yourallegiance to your editor - the Next Chapter!

Summary

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