unix talk 2010

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UNIX Talk 2010

Reference Notes

Dedicated to students of CENG & CSCI 3150.

(the same handout as the one for CEG UNIX Talk, Jan 2010)

Last update: September 13, 2010.

Prepared by: Dr. WONG, Tsz Yeung.

1

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CONTENTS 2

Contents

1 UNIX and Our Department 5

1.1 Your Rights - How Much Data Can You Own? . . . . . . . . . 6

1.1.1 Keep an eye on your quota . . . . . . . . . . . . . . . . 9

1.2 Computing Facilities - UNIX-Like Workstations . . . . . . . . 10

1.2.1 Console login . . . . . . . . . . . . . . . . . . . . . . . 10

1.2.2 Remote login . . . . . . . . . . . . . . . . . . . . . . . 10

1.3 Network Services in Our Department . . . . . . . . . . . . . . 12

1.3.1 Walkthrough: SSH login from a Windows PC . . . . . 12

1.3.2 Web service: hosting your personal homepage . . . . . 19

1.3.3 Email and email forwarding . . . . . . . . . . . . . . . 19

1.4 A Short Summary . . . . . . . . . . . . . . . . . . . . . . . . . 20

2 File Processing 21

2.1 File & Directory . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.1.1 Create and Remove File . . . . . . . . . . . . . . . . . 21

2.1.2 View Files Content . . . . . . . . . . . . . . . . . . . . 22

2.1.3 Move and Copy Files . . . . . . . . . . . . . . . . . . . 23

2.1.4 File Type . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.1.5 Create and Remove Directory . . . . . . . . . . . . . . 26

2.1.6 Change Directory . . . . . . . . . . . . . . . . . . . . . 26

2.1.7 View Directorys Content . . . . . . . . . . . . . . . . 27

2.1.8 Special Directories . . . . . . . . . . . . . . . . . . . . 27

2.1.9 Redirection and Pipe . . . . . . . . . . . . . . . . . . . 29

2.2 File Permission . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.2.1 Read, Write, Execute Modes . . . . . . . . . . . . . . . 31

2.2.2 Changing Modes . . . . . . . . . . . . . . . . . . . . . 322.2.3 Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3 Process Management 34

3.1 Display Process Details . . . . . . . . . . . . . . . . . . . . . . 34

3.2 Kill Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.3 Foreground and Background Job . . . . . . . . . . . . . . . . 35

3.3.1 Create Background Job . . . . . . . . . . . . . . . . . . 36

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CONTENTS 3

3.4 Kill Background Job . . . . . . . . . . . . . . . . . . . . . . . 36

4 Printing in Department 37

4.1 Printing Files . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.2 Printing Queue . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.3 Delete Print Job . . . . . . . . . . . . . . . . . . . . . . . . . 38

4.4 Print Quota . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5 UNIX Tools 39

5.1 Internal Communication . . . . . . . . . . . . . . . . . . . . . 39

5.1.1 talk . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395.1.2 write . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5.1.3 finger . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5.2 Password and Personal Details . . . . . . . . . . . . . . . . . . 40

5.2.1 passwd & yppasswd . . . . . . . . . . . . . . . . . . . 40

5.2.2 chfn . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.3 Text Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.3.1 VI and VI IMproved . . . . . . . . . . . . . . . . . . . 40

5.3.2 PICO . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.4 Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

5.4.1 SFTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

5.4.2 PINE and ELM . . . . . . . . . . . . . . . . . . . . . . 41

5.4.3 TIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.4.4 LYNX . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.4.5 WGET . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5.5 Compression and Archives . . . . . . . . . . . . . . . . . . . . 43

5.5.1 ZIP, UnZip and Zipinfo . . . . . . . . . . . . . . . . . . 43

5.5.2 GZIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445.5.3 Tar and GNU Tar . . . . . . . . . . . . . . . . . . . . . 44

5.6 Image Manipulation . . . . . . . . . . . . . . . . . . . . . . . 45

5.6.1 XV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.6.2 GIMP . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.7 Document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

5.7.1 GV and GhostView . . . . . . . . . . . . . . . . . . . . 46

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CONTENTS 4

5.7.2 ACROREAD . . . . . . . . . . . . . . . . . . . . . . . 46

5.7.3 StarOffice . . . . . . . . . . . . . . . . . . . . . . . . . 46

5.8 Dictionary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

5.9 Manual Page . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

A Installing the SSH Client Program 48

B SHELL command 50

C VI command 51

D Pico Command 55

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1 UNIX AND OUR DEPARTMENT 5

1 UNIX and Our Department

The rule of thumb to survive in our department is to know and to workwith UNIX. UNIX-like systems are everywhere in this department.

Mac is a UNIX-like system;

Linux is a UNIX-like system; and

UNIX itself.

UNIXStorageServers

EmailServer

WebServer

Samba Servers

(smb1, smb2, etc)Windows

PCWindows

PC

UnixWorkstation

UnixWorkstationUnix

Workstation

H Drive

Mac PCsMac PCsMac PCs

UsingSSH

gateway

(gw.cse)

UsingSSH

Internal Network

External Network

Mac PCsMac PCsLinux

PCs

Figure 1: Networking and services in our department.

Figure 1 shows you the fact that nearly all services in our department

are centered around the UNIX storage servers. They contain your user

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accounts and your emails (and, of course, there are tons of other things

that you may not be interested).

If you are still not convinced that you do not need any knowledge about

UNIX systems, please take a look at the following list of inconvenient

truths.

The Windows PCs in our department only allow you to access files

stored in your user account, but not other services such as checking

your disk quota.

You cannot use the H drive in the Windows PCs in your home.Only SSH programs can help you, and you may also need those UNIX

commands, too.

You cannot check your print quota in the Windows PCs. You can only

do so in UNIX.

For some courses, you can only work in UNIX-like systems, e.g., CSCI

& CENG3150, CENG3430, CENG3470, CSCI3170, CSCI5470, etc.

So, why not learning how to work with the UNIX system?

1.1 Your Rights - How Much Data Can You Own?

As a matter of fact, you are entitled to host more than 2GB of data in our

department. However, the access to the data is quite restricted. Figure 2

has shown the storage space and the corresponding ways to access them.

UNIX personal account. This is the primary place for you to store

your source code, lecture notes, etc. The good about this storage is

not only big, but also is a shared place between the UNIX workstation

and the Windows PCs.

In order words, after you have copied a source code file from a Windows

PC to the personal account, you can immediately modify it in a UNIX

workstation!

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UNIX PersonalAccount

2GB

WindowsPC

WindowsPC in lab

WindowsProfile50MB

Email50MB

N Drive

H Drive

UnixWorkstation

UnixWorkstationWorkstation

Your home directory

Directory:/var/mail/[login ID]

/public100MB

Directory:/public

Figure 2: The storage service provided to every user in the department.

Windows profile. The second attractive place is the Windows profile.

It stores your Windows account data: your desktop, your wallpaper,

etc. With this storage, you can log in at different Windows PCs but

have the same desktop and the same wallpaper.

However, the quota is just not enough and will easily be used up.

Therefore, remember to always move files in your desktop to the UNIX

personal account.

Email. Emails are stored inside the UNIX storage system and therefore

can only be accessed through UNIX workstations only, not Linux

nor Mac. E.g., if you were the user tywong, then you can find your

email at the location /var/mail/tywong.

It is always interesting to know that all your emails are stored as ONE

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Story-Telling Time - the /public

You may wonder why there is a public, sharable storage with 100MB

space only. As a matter of fact, there are historical reasons.

In the late 90s, every undergraduate student was only given a UNIX

personal account of5MB space only. Now, think about it: what if

I need to process a data file of 5MB? What if I need to produce an

output of 5MB? (Yes, there were such needs. In my data structure

course, I was told to read in a 1MB file. I needed to build some datastructures over the data and I also needed to output it.)

To solve such a problem, a publicly accessible, huge storage place is

born. Nevertheless, people started to abuse such a place, e.g., sharing

MP3, games, etc.

FILE ONLY. Those who are interested can take a look inside and

guess why it is so different from those you found using the web mailservice.

/public. The way that we name is because of its location: in the

workstations, the location of the 100MB-space is /public.

The special thing about this storage is that everyone can share files

there. Occasionally, you will find some good stuffs there. Of course, the

/public directory will be cleaned up everyday.

Your Responsibility.

A user shall not store any materials with offensive content in

his/her computer account and /public in Unix workstations,

or any materials that infringe the laws regarding Copyright,

Patent and Trademark.

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For other responsibilities, you are required to read the following page:

http://wiki.cse.cuhk.edu.hk/tech/regulations/main

1.1.1 Keep an eye on your quota

Now, you know that you are only given limited resources. It is your respon-

sibility to keep track on your disk usage. But, what if you have used up your

disk quota?

If you have used up your disk quota, you cannot add any new

data/files into your account.

Whats the big deal? You may ask. The problems are:

You cannot save any work in-progress.

You cannot compile any programs.

Well, the above problems are good sources of strange bugs whileyou are working on your assignments.

To monitor your quota in your UNIX personal account and /public,

please invoke:

quota -v

The above command displays your current usage and the quota imposed.

For the usage of your email storage, you need another way:

du -k /var/mail/[your login name]

The above command measures how many KBytes you have used to store

the emails.

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1.2 Computing Facilities - UNIX-Like Workstations

The lists of UNIX-like workstations are given as follows.

Machine OS Hostname

Sun Ultra Solaris 8 sparc1 - sparc30

Linux Ubuntu 8.04 / 9.04 server linux1 - linux9

Ubuntu 10.04 64-bit server linux10 - linux15

Mac Mac OS X / Darwin mac1 - mac12

There are two ways to go into the machines and both ways require yourUNIX credential.

What is a credential?

It means your identity and is usually presented as the (login

ID, password) pair.

1.2.1 Console login

The phrase console login means you log in the workstation in front of the

workstation. However, except the Mac workstations, you can hardly find a

console in the laboratory; They are hidden by our system administrators.

An analogy. You are doing the console login action in front of your

Windows PC everyday.

1.2.2 Remote login

On contrary, remote login means that you log in the workstation from

another workstation/PC (not in front of the target workstation). There are

several forms of remote logins.

Windows: remote desktop.

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How many user accounts do you have?

Since the first day you entered our department, you had been

given two accounts: the UNIX account and the Windows

account.

The two accounts are different although they have the same

login name. In other words, when you changing the password

of the Windows account, you are not changing the password

of the UNIX account, and vice versa.

The UNIX account governs many things:

- access to workstations;

- access to printers;

- access to email service;

- access to the department VPN service;

- access to some course web pages;

However, the Windows account only governs the access to

Windows PC only.

UNIX-like workstations: ssh and telnet (depreciated because

it is not secure).

In most of the cases, we will use a Windows PC to remotely log in

a UNIX workstation using a SSH client program. All UNIX worksta-

tions, Mac workstations, and Linux workstations support the SSH service.

In the next section, we will show you how to do so.

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1.3 Network Services in Our Department

For further information, please refer to the following link:

https://www.cse.cuhk.edu.hk/corner/tech/guide/network.html

Mainly, there are three network services you will be interested:

Remote login using SSH,

Web server, and

Email.

1.3.1 Walkthrough: SSH login from a Windows PC

The word SSH is a abbreviation of the name Secure SHell and we usually

use SSH as a verb. E.g., you cannot ssh to a Windows PC. Figure 3

shows how to ssh from your home to a UNIX machine. We describe the

steps involved in the following context.

Installing the SSH client program.

Sorry, on behalf of Uncle Bill, all versions of Windows do not

have any SSH client program pre-installed.

Dont worry. Our university has purchased the license of a SSH client pro-

gram. Every Windows PC in our department has such a program installed.

Nevertheless, if you are connecting from home, you will need the installation.

For the details, please refer to the Appendix of this handout.

SSH to the gateway first if you are outside CSE network

If you are using a connection outside the CSE department, that means:

Commercial ISPs, such as PCCW and HKBN;

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WindowsPC in home

UnixWorkstation

UnixWorkstationUnixWorkstations

Mac PCsMac PCsMac PCs

gateway

(gw.cse)

Internal

Network

Mac PCsMac PCsLinux

PCs

SSH to gw.cse.cuhk.edu.hk

SSH to a workstationin the gateway

WindowsPC in Lab

SSH to a workstationdirectly.

Figure 3: How and where to ssh?

CUHK network service, including the ClassNet, the Resnet, the VPN,

and the CUHK Wifi service;

ERGWAVE Wifi service;

then, you must go through the department gateway in order to remotely log

in the workstations. In Figures 4-8, step-by-step guidelines will be given.

Step 1, Figure 4. Launch the SSH program and click the Quick

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Story-Telling Time - the gateway

Before 2000, all workstations and Windows PCs in our department

were directly connected to the outside world. I used to remotely

control a Windows PC in the lab using VNC from my home.

Nevertheless, this measure gave a window to hackers and we did suffer

from an attack. After such an attack, our department tightened our

network. The gateways were installed since that attack.

Connect button.

Step 2, Figure 5. Type in the name of the department gateway and

your login name.

Step 3, Figure 6. Type in your UNIX password.

Step 4, Figure 7. If everything is smooth, you will be inside the gateway

machine. Else, you will be prompted to enter the password again. It isbecause you have typed either a wrong login name or a wrong password.

Now, you are one step away from logging in the workstation. The next

step is to type the following command:

ssh sparc1

The above command means that you want to ssh to the UNIX work-

station sparc1. Next, you will be asked to enter your password. Yes,

you have to type in the same UNIX password again.

tywongsparc1s password:

Step 5, Figure 8. Great! You are now inside the UNIX workstation

sparc1. Congratulations!

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Figure 4: Step 1. Click the Quick Connect button.

Figure 5: Step 2. Host Name = gw.cse.cuhk.edu.hk; User Name = your

login name.

Figure 6: Step 3. Remember, type your UNIX password, and it is case-

sensitive.

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Figure 7: Step 4. Now, you are inside our department gateway.

Figure 8: Step 5. Congratulations! You are in the UNIX workstation sparc1.

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SSH to the workstations directly if you are inside CSE network

Then, the procedure becomes very easy: just skip the gateway.

Step 1. Launch the SSH program and click the Quick Connect but-

ton.

Step 2. Type in the name of the workstation you want to reach, e.g.,

sparc1 or mac1, together with your login name. Right, you can omit

.cse.cuhk.edu.hk (and thanks for the work done by our administra-

tors).

Step 3. Type in your UNIX password.

Step 4. Bingo! You are now inside the UNIX workstation.

That is not the end of the SSH program, you can do many things:

Use the UNIX environment with commands, and such an interface is

called the command line interface, CLI for short.

Use another feature of the SSH program to transfer files to and from

your UNIX account. Figures 9 and Figure 10 have shown you how.

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Figure 9: You can launch the Secure File Transfer by clicking New File

Transfer.

Figure 10: Left Hand Side: your local disks. Right Hand Side: the home

directory of your UNIX account.

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1.3.2 Web service: hosting your personal homepage

To host your personal homepage, the following steps can help you.

1. Create the directory www in your UNIX account.

2. Mark the directory as readable by all people with the following

command:

chmod 711 www

(We will say more about the chmod command later.)

3. Then, create your homepage inside that directory.

4. Last, you can view your homepage. E.g., if your login name were

tywong, then the location of your homepage would be:

http://www.cse.cuhk.edu.hk/~tywong/

1.3.3 Email and email forwarding

By the way, do you know that you have a department email address E.g., if

your login name were tywong, then your email address would be:

[email protected]

A truth: most tutors and teachers try to contact you using your depart-

ment email address only. Therefore, in order to guarantee you are not going

to miss any emails from our department, our system administrator has setup an email forwarding service.

The configuration file about this service is called .forward and it is pre-

installed inside your home directory of your UNIX account. The .forward

file is a plaintext file and an example content of the .forward is as follows.

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[email protected]

The content specifies that every email sending to your department email

address will be forwarded to the email address [email protected].

Can I disable the email forwarding service?

Sure. To disable the service, you just have to remove the .forward file.

How Can I check the department emails?

The simplest way is to use the web mail system in the following link:

http://webmail.cse.cuhk.edu.hk/

More advanced ways will be using the UNIX commands and we will show

you later.

1.4 A Short Summary

This is not the end of the basics of the usage of UNIX in our department.

For more details, you are welcome to visit the following site:

http://www.cse.cuhk.edu.hk/corner/

In the next chapter, we start introducing you the UNIX commands.

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2 FILE PROCESSING 21

2 File Processing

In this section, we are going to introduce the most important thing in UNIX,that is File. File is everything in UNIX including directory, hard disks, and

even printers.

In the following text, we would like to introduce the processing of files and

directories. Including creation, removal, moving and copying, as well as per-

mission policy in files in UNIX system.

2.1 File & Directory

2.1.1 Create and Remove File

- We can use the following methods to create files

Using command touch

touch is a command that can create empty files (an empty file

is a file contains zero byte). If the file that is being touched

already exists, it will only change the file access and modifi-cation times.

To use touch:

touch [filename]

Using text editor

Text Editor is a program that can save the text we type.

- To remove files, we can use the command rm. To invoke:

rm [filename]

rm can remove every file. So please be careful:

rm * can be dangerous !!!

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2.1.2 View Files Content

In this subsection, we will talk about text file (or ASCII file).

- Using Text Editor

Text Editor not only can view a files content, it can also modify a

files content.

- Other than Text Editor

cat can be used to display a files content (Not a pet like dog:). Toinvoke:

cat [filename(s)]

It can be used to concatenate several files into one.

e.g. cat file1 file2 file3 > aLargeFile

more is a useful tool to browse through a text file. It is much better

than cat. cat will dump out all the content. But, more can fit

the text file into pages. To invoke:

more [filename]

Below shows some simple command for more

b page up

f page down

space page downenter go down a line

/ search

q quit

less is the opposite of more (just kidding!!). less is a similar tool as

more. It supports more commands than more. To invoke:

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less [filename]

Below shows some simple command for less

b page up

f page down

q quit

scroll up

scroll down

/ searchg Go to the first line

G Go to the last line

ng Go to the nth line

head can display the first N lines of a file. It can be adjusted to display

1 to N lines. The following example display the first 5 lines of the

file aFile.

e.g. head -5 aFile

tail is the opposite of head (This time is not a joke). It displays the

last N lines of a file.

e.g. tail -8 aFile

2.1.3 Move and Copy Files

- We can move a file from one place to another by using mv. We can

also use mv to change a files name. To invoke mv (move):

mv [source] [destination]

e.g. mv 3150.cpp 3150/example.cpp

This example moves 3150.cpp into the directory 3150

and the file name is changed to example.cpp.

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e.g. mv 3150.cpp 3150/

This example has the similar effect as the previous one, ex-

cept that the file name is still 3150.cpp.

e.g. mv 3150.cpp 3150.cpp.backup

This example changes the filename 3150.cpp into 3150.cpp.backup.

- We can copy a file to other places by using the command cp. To invoke

cp (copy):

cp [source] [destination]

e.g. cp 3150.cpp 3150.cpp.backup

This example copies a backup of 3150.cpp and names the

new file as 3150.cpp.backup.

e.g. cp 3150.cpp 3150/assg1/

This example copies 3150.cpp into the directory 3150/assg1.

e.g. cp -R 3150/ passed course/

This example copies all the files inside 3150 including sub-

directory into the directory passed course. The argument

-R is needed if you want to copy all the sub-directories inside

3150.

2.1.4 File Type

- In DOS/Windows, the type of file is usually determined by its file

extension. But in UNIX, the file extension is useless (or not significant).

- We have a very useful tool which can determine the file type easily. It

is called file. To invoke file:

file [filename]

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e.g. file hello.gif

return: hello.gif: GIF file, v89

- Remember, file extensions in UNIX is not so important. Therefore, we

need the file command to help us in determining file types. E.g.,

mv hello.gif hello.mp3

file hello.mp3

return: hello.mp3: GIF file, v89

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2.1.5 Create and Remove Directory

Directory is an important file type in UNIX system. The above commands

such as mv, cp, etc are also applicable since directory is also a file. However,

its creation, removal as well as content are special.

- We can create a directory by using mkdir. To invoke:

mkdir [directory name]

e.g. mkdir unixTalk

This creates a directory called unixTalk.

- We can remove a directory by 2 ways:

1. By using rmdir. To invoke:

rmdir [directory name]

This command fails if the target directory contains files. In this

case, we should choose the second method.

2. By using rm -r. To invoke:

rm -r [directory name]

This command will ask for confirmation of the removal of all the

files in the directory.

2.1.6 Change Directory

We can browse through the directory structure by a famous command. It is

cd (stand for Change Directory). To invoke:

cd [directory name]

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2.1.7 View Directorys Content

As directory is also a file, we can read its content. However, directory is a

special type of file, we need a special and famous command to read it. It is

ls. To invoke:

ls [argument] [directory or files]

e.g. ls -l assignment

This example will list the directory assignment in a long format.

There are a lot of arguments for ls. Here, we describe some of

them.

-a List all entries including hidden files.

-l List all entries in long format.

-R List all files and sub-directories recursively.

2.1.8 Special Directories

We will describe 3 kinds of special directory: . (a dot), .. (two dots) and .

Below shows a table of these special directory:

. current directory

.. parent directory

home directory

e.g. ls -l .

This command lists all the entries in current directory.

e.g. cd ..

This command browses to the parent directory.

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e.g. cd

This command browses to the home directory of the current user.

e.g. cd tywong

This command browses to the home directory of tywong.

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2.1.9 Redirection and Pipe

- In UNIX, we have 3 special (or default) files. They are namely STDIN

(standard input), STDOUT (standard output) and STDERR

(standard error). The following is the description of these 3 files.

STDIN It stands for the input of a program. Typically, the standard

input is the keyboard.

STDOUT It stands for the output of a program. Typically, the

standard output is the screen.

STDERR It stands for the output of the error message(s) of a pro-

gram. Typically, the standard output is also the screen.

- We summarize these with the below analogy.

STDIN keyboard

STDOUT monitor

STDERR monitor

- We can change the STDIN and STDOUT of a program by using redi-

rection and pipe file

1. Redirection

We have 3 kinds of redirections: >, < and >>.

The > symbol is used in this way:

[program] > [file]

The STDOUT of the program will be replaced by the targetfile. If the file already exists, we add a ! after >.

e.g. ls -l >! output

This command will create(or replace) the file with

name output. The file output will contain the

result of ls -l.

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The symbol >> is used in this way:

[program] >> [file]

This symbol is similar to >. However, instead of erasing all

the data in file, >> appends the STDOUT to file.

The Replace STDOUT and flush to a file

>> Replace STDOUT and append to a file

< Replace STDIN by reading content of a file

2. Pipe File

A pipe File is a symbol, |. The usage is:

[program1] | [program2]

It is a special file. It acts as a temporary storage to store the STD-

OUT of program1. This storage will then serve as the STDIN of

program2.

e.g. ls -l | more

The ls -l will give its STDOUT to the pipe. Then,

more will read the pipe as its STDIN. The result of this

example is to generate a page-separated directory con-

tent.

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2.2 File Permission

In this sub-section, we would like to discuss the permission policy of files in

UNIX system.

2.2.1 Read, Write, Execute Modes

Below is a typical result of ls -l:

-rw------- 1 tywong lec 11 Jan 1 00:00 test.c

The first 9 character, i.e.

-rw-------

are the permission that is set to the file. If all the states are on, the permission

will be:

-rwxrwxrwx

The first rwx stands for the permission for the owner of the file.

The middle rwx stands for the permission for the group of the owner.

The last rwx stands for the permission for other users.

From the following example:

-rw------- 1 tywong lec 11 Jan 1 00:00 test.c

We know the following information about this file.

Owner tywong

Group lec

Permission for User Read, Write

Permission for Group No permission grantedPermission for Other No permission granted

The rw- permission of user means that the user is allowed to Read and Write

the file. However, he/she is not allowed to eXecute the file. The users of the

same group and other users are not allowed to Read, Write or eXecute the file.

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2.2.2 Changing Modes

UNIX system has a very useful command to change permission of a file. It

is chmod (change mode). The format is:

chmod [absolute modes] [filename], or

chmod [symbolic-mode-list] [filename]

1. Absolute Modes

The absolute mode contains 3 numbers between 0 and 7. The cal-

culation of the mode is carried out like this:

For example, if we want to change to the following mode:

rw- --- --- = 600 (absolute mode)

We convert the permission into a 9 bits representation, i.e.

rw- --- --- = 110 000 000

Then, we group the bits 3 into 1 group, and convert it into a base 8

number, i.e.

rw- --- --- = 110 000 000 = 6 0 0

The mode calculation is completed, and then we can type:

chmod 600 test.c

to change mode.

e.g. rw- r-- r-- = 110 100 100 = 644

e.g. rwx r-x r-x = 111 101 101 = 755

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2. Symbolic Mode

This mode uses symbols for changing mode. For example, you want

all people to view your photo. By absolute mode, you need to change

mode to 644. But, using symbolic mode, it is like this:

chmod a+r myPhoto.jpg

a+r means that All(a) Add(+) Read(r) permission.

Or, you have written a program and want to share with all your Y09classmates only. you can:

chmod g+rx myProgram

a+r means that Group(g) Add(+) Read(r) and eXecute(x)

permission.

The following table shows the symbols used in symbolic mode.

r read permission

w write permission

x execute permission

a all users

u owner(user)

g group

o other

+ add permission(s)

- remove permission(s)

2.2.3 Remarks

Directory should be EXECUTABLE if you want to cd to it.

Directory should be READABLE if you want to ls it.

Program must be EXECUTABLE.

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3 PROCESS MANAGEMENT 34

3 Process Management

Process is another important component of UNIX system. Every programwhich is executing is a process (you will learn a more formal definition later).

In this section, we are going to introduce the management of processes.

3.1 Display Process Details

Whenever a process is created in UNIX, an unique ID will be created for

the process also. It is called Process ID (PID). We can locate a process by

searching the program name as well as PID. The following text introducessome of the commands and tools.

top

top is a tool that displays information about the processes including

PID. It is an interactive one and updates the cpu information periodi-

cally.

ps

ps is also a tool that displays information about processes. But, it

only shows the jobs that are running on the working terminal. How-

ever, if you type the command like the following, you can get all the

processes PID that belong to you in a single machine.

ps -u [username]

w

w cannot shows the PIDs of running processes. However, it can display

all current active jobs in the machine.

3.2 Kill Process

There are cases that process will not terminate even if you use Ctrl+C. One

of the method is to switch the machine off. However, this is FORBIDDEN

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in our department as you will kill other peoples jobs also. UNIX is a nice

system; it provides ways for you to kill those stubborn processes.

kill

kill sends signal to your target process in order to let it to rest in

peace. The format is :

kill [PID]

If the process is so tough that it is still not being killed, try to add

an argument -9 to kill.

kill -9 [PID]

top

top has a option for users to kill processes. Here, we provide some

options of top.

k kill

u list specific users job

3.3 Foreground and Background Job

There are cases that you are running a job which consume a long period

of time (several hours) to finish. You have dated your boy/girl friend, you

cannot wait for it to finish. However, if you logout your machine, the terms

and jobs will be killed too!!!! What should you do??

No panic!! Those ordinary jobs that you are running are called foreground

jobs. UNIX has another type of job which is called background job. This

kind of job can be run behind the login terminals.

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3.3.1 Create Background Job

To create background job, there are 2 ways.

Create a Background One

To create a background job, just type & at the end of the command.

e.g. /usr/local/bin/netscape4.7 &

Change Foreground to Background

1. Type Ctrl+Z in the terminal that the foreground job is running.

2. The job is now changing to a suspended job.

3. Type bg (Back-Ground) onto the terminal that the suspended job

is on, a background job is created.

3.4 Kill Background Job

1. You can type fg in the terminal that you create background jobs. Then,

you can press Ctrl+C to kill it. If the term does not exist, then

2. You can use the methods introduced in the previous subsection.

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4 PRINTING IN DEPARTMENT 37

4 Printing in Department

Our department has provided us 7 postscript laser printers and 2 dot matrix

printers for us to use. Their locations are:

Printer Name Location Type

ps SHB924 Laser

ps2 SHB924 Laser

ps3 SHB904 Laser

ps4 SHB122 Laser

cps SHB122 Color Lasercps1 SHB924 Color Laser

cps2 SHB924 Color Laser

openlab SHB904 Dot Matrix (Plaintext only)

declab SHB924 Dot Matrix (Plaintext only)

4.1 Printing Files

We can print files in UNIX with this command:

lpr -P[printer name] [filename]

This command can only print plain text files and postscript files (usually

with extension .ps).

4.2 Printing Queue

As the printers are shared among several hundreds of classmates, we will

need to queue up in order to get the printing service. Once you send the job

to the printer, you can check the queue of the printer:

lpq -P[printer name], or

showprint

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4 PRINTING IN DEPARTMENT 38

4.3 Delete Print Job

If your job is not processing (or printing), you can dequeue your job from

the printer by:

lprm -P[printer name] [Job ID] [username]

4.4 Print Quota

Printing in our Department costs money. Initially, each undergraduate has

50 quotas. After each semester, 50 more quotas will be added. Each quota

costs $0.30. Below show the charges for printing.

ps (Duplex) 1 quota

ps2 (Duplex or non-duplex) 1 quota

ps3 (Duplex or non-duplex) 1 quota

ps4 (Duplex) 1 quota

cps 5 quota

cps1 5 quotacps2 5 quota

openlab free of charge

declab free of charge

To check how many quotas are still left, use this:

printquota

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5 UNIX TOOLS 39

5 UNIX Tools

In this section, we introduce some useful tools in UNIX.

5.1 Internal Communication

This category of tools is for communicating with people within the same

network.

5.1.1 talk

This tool allows 2 people to chat with each other. But, it only allows 2

people.

talk [username]

5.1.2 write

This tool allows an user to send message to other users.

write [username] [terminal]

5.1.3 finger

It is not a communicating one, but it allows users to see other users infor-

mation

finger [username]

e.g. finger tywong

Login name: tywong In real life: Wong Tsz Yeung

Directory: /uac/lec/tywong Shell: /bin/tcsh

On since Jan 4 00:23:02 on pts/1 from 137.189.90.237

Unread mail since Sun Jan 3 23:53:43 2010

Plan:

I teach OS.

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5 UNIX TOOLS 40

5.2 Password and Personal Details

5.2.1 passwd & yppasswd

You can change your UNIX password by using passwd. In our department,

passwd and yppasswd are the same program. To invoke:

passwd or yppasswd

5.2.2 chfn

You can change your finger information by using chfn. To invoke:

chfn

The above programs need your current UNIX password in order to change

your personal informations.

5.3 Text Editor

Text editor is an important tools. It enables us to compose a text file such as

email, programs, etc. There are a lot of text editors in UNIX. We introduce

two useful text editors.

5.3.1 VI and VI IMproved

VI is nearly the most powerful text editor in UNIX system, and Vi IM-

proved (VIM) is the VI-enhanced version. VI has 2 modes, one is Com-

mand Mode and another one is Edit Mode. The detailed commands will

be shown in the appendix. To invoke VI or VIM:

vi [filename] or vim [filename]

where the filename can be omitted.

5.3.2 PICO

PICO is a less powerful text editor than VI or VIM. However, it is easy to

use and has a lot of useful commands. The detailed commands will be shown

in the appendix. To invoke PICO:

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5 UNIX TOOLS 41

pico [filename]


5.4 Internet

This section introduces a lot of tools that are related to the Internet.

5.4.1 SFTP

SFTP stands for Secure File Transfer Protocol. The tool allows you to

login to the target host, and can download or upload files from that host.To invoke sftp:

sftp [hostname or IP address]

Below shows some commands of sftp

bye close connection

cd [pathname] change the directory in the remote host

lcd [pathname] change the directory in the local hostget [filename] download one file

mget [filename(s)] download multiple files

put [filename] upload one file

mput [filename(s)] upload multiple files

ls list file entries in hosts

prompt turn prompting off

5.4.2 PINE and ELM

PINE and ELM are mail reader and composer. You can read and reply

your email in these 2 programs.

PINE is a program for Internet News and Email. It is a more convenient

Email program. It supports attachment also. To invoke PINE:

pine

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5 UNIX TOOLS 42

ELM is a not as user-friendly as PINE. However, it supports command line

to send mail. To invoke ELM:

elm [arguments] [email address]

Notes: you can omit arguments and email address

e.g. elm -s "Just to Say HI" [email protected]

This will send an email to [email protected] with a subject

Just to Say HI.

5.4.3 TIN

It is an Internet News program. It allows you to read, reply and subscribe

to newsgroups. To invoke tin:

tin

Below shows some commands of tin.

y Browse groups on server or Browse subscribed groups

s subscribe group

u unsubscribe group

w post a news (or thread)

f followup in a thread

go down one level in the newsgroup

go up one level in the newsgroup

scroll up

scroll down

5.4.4 LYNX

It is a famous text mode web program. It allows you to surf the Internet,

but not Javascript support. To invoke lynx:

lynx [hyperlink]

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5 UNIX TOOLS 43

5.4.5 WGET

It is a very handy tool that allows you to download stuffs with hyperlinks.

It also provides some great features, such as downloading from a list of hy-

perlinks and recursively downloading a web site.

wget [hyperlink]

e.g. wget http://www.cse.cuhk.edu.hk/index.html

This command downloads the file index.html from our depart-ment.

e.g. wget -i list.txt

This command instructs wget to download from the list of

URLs stored in list.txt.

e.g. wget -l 2 -R http://www.cse.cuhk.edu.hk/

This command instructs wget to start downloading recursivelyfrom our department homepage, with a maximum depth of 2 lev-

els.

5.5 Compression and Archives

There are a lot of compression tools in UNIX. We introduce some popular

ones.

5.5.1 ZIP, UnZip and Zipinfo

ZIP is very popular in Windows. The UNIX Zip is compatible with the zip

program in Windows environment. To use Zip:

zip [destination file (zip file)] [file(s) to compress]

unzip [destination file (zip file)]

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5 UNIX TOOLS 44

If you want to compress directory, then you need to argument -r.

zip -r [destination file (zip file)] [directory(s) to compress]

zipinfo is to view the content of a zip file. To invoke :

zipinfo [zip file]

5.5.2 GZIP

GZIP is another compression tools in UNIX. To use GZip:gzip [filename]

gunzip [filename]

e.g. gzip hello.cpp

A compressed file hello.cpp.gz will be created and hello.cpp will

be deleted.

5.5.3 Tar and GNU Tar

Tar is not a compression tool, instead it is a tool to create an archive. An

archive stands for a package of files. To use Tar or GNU Tar (gtar):

tar -[arguments] [tar file] [filename(s)]

gtar -[arguments] [tar file] [filename(s)]

Below shows some arguments for tar and gtar.

c Create tar file

t View a tar files content

x Extract a tar files content

f Specify the name of a tar file

v View the name of each file being processed by tar

z Use Gzip in Creating and Extracting tar file

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5 UNIX TOOLS 45

e.g. tar -cf abc.tar test.cpp test.html test.c

This command will create a tar file abc.tar. The tar file contains

test.cpp, text.html and test.c.

e.g tar -tf abc.tar

This command will list the files contained in abc.tar.

e.g. tar -xf abc.tar

This command will extract the abc.tar.

e.g. gtar -czf abc.tar.gz test.cpp test.html test.c

This command will create a gzipped tar file named abc.tar.gz.

e.g. gtar -xzf abc.tar.gz

This command will extract the abc.tar.gz.

5.6 Image Manipulation

In this section, we introduce some image manipulation tools in UNIX.

5.6.1 XV

XV allows your to view, crop and print your images. It supports a lot of

image format such as JPEG, GIF, TIFF, BMP, etc. To invoke XV:

xv [image filename]

where the image filename can be omitted.

5.6.2 GIMP

GIMP stands for GNU Image Manipulation Program. Or, it is the UNIX

PhotoShop. It has the similar power as PhotoShop in Windows. To invoke

GIMP:

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5 UNIX TOOLS 46

gimp [image filename]

where the image filename can be omitted.

5.7 Document

In this section, we introduce a few document viewers and composers in UNIX.

5.7.1 GV and GhostView

GV and Ghostview are used to view PostScript files (usually with exten-sion .ps). To invoke:

gv [filename]

ghostview [filename]


5.7.2 ACROREAD

AcroRead is the AcroBat Reader. It is capable of opening PDF file. To

invoke it:

acroread [filename]

The filename can be omitted.

5.7.3 StarOffice

StarOffice is a office suite implemented in JAVA. It can open nearly all kindsof MicroSoft Office files. The setup of StarOffice is a little bit troublesome.

For reference, please go to:

http://www.cse.cuhk.edu.hk/corner/tech/doc/ht/typeset/#soffice

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5 UNIX TOOLS 47

5.8 Dictionary

We have a dictionary installed in our UNIX system, the webster. To invoke:

webster [word]

The word can be omitted.

5.9 Manual Page

Last but not least, we introduce you the manual page in UNIX. To invoke:

man [program name]

e.g. man ls

The manual page (or man page) of ls will be shown.

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A Installing the SSH Client Program

Step 1. Go to ITSC homepage:

http://www.cuhk.edu.hk/itsc/index-en.html

Then, select the option as shown in Figure 11.

Figure 11: Step 1. Go to ITSC homepage and select the Useful Tools and

Links.

Step 2. Select SSH as shown in Figure 12.

Step 3. After some nexts and agrees, you will reach the page shown

in Figure 13. Download the first two exe files. The first exe file isthe primary installer. Please install it first. The second exe file is the

update. Please install it after the first one.

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Figure 12: Step 2. Select the Secure Remote Access with SSH.

Figure 13: Step 3. Download two exe files.

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B SHELL command

This following commands are applicable in bash and tcsh.

Ctrl + b move to left by 1 character

Ctrl + f move to right by 1 character

Ctrl + a move to the beginning of a line

Ctrl + e move to the end of a line

Ctrl + u cut and copy all the characters on the left of the cursor

Ctrl + k cut and copy all the characters on the right of the cursor

Ctrl + y paste the copied characters on the right of the cursor

Ctrl + d delete the character at the cursor position

Ctrl + h backspace

Ctrl + s Scroll lock (lock keyboard)

Ctrl + q Unlock scroll lock

Ctrl + l Clear Screen

history show all the commands previously invoked

jobs show all the jobs running or suspendedtab auto completion

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C VI command

Cursor movement Commands

------------------------

j - down 1 line

k - up 1 line

h - left 1 char

l - right 1 char

^f - forward 1 screen

^b - backward 1 screen

^u - up half screen

^d - down half screen

H - top (Head line) of screen

L - bottom (Last line) of screen

^y - scroll down 1 line at top of screen (cursor not move)

^e - scroll up 1 line at bottom of screen (cursor not move)

0 - (zero) - first char of current line

$ - last char of current line

w - move to start of next wordW - move to start of next WORD (white-space delimited)

e - move to end of word

E - move to end of WORD

b - move back to previous word

B - move back to previous WORD

f - find char c in current line in forward direction

F - find char c in current line in backward direction

; - repeat last Find in same direction

, - repeat last Find in opposite direction

% - find matching () [] {}

m - mark current line -- can be a to z

- goto line with mark

G - goto last line of file

1G - goto 1-st line of file

123G - goto line number 123

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Insert Commands (insert mode terminated by )

---------------

a - append after curser

i - insert before cursor

A - Append after end of line

I - Insert before 1st non-white space

o - open an empty line after current line for insert

O - Open an empty line before current line for insert

Other Commands (replace/change-command terminated by )

--------------

r - replace current character by char

R - replace characters until pressed

s - substitute current char until pressed

S - substitute current line until pressed

cw - change up to end of word until pressed

cW - change up to end of WORD until pressed

dw - delete word

dW - delete WORD

dd - delete line

yw - yank (store into buffer) 1 word

yy - yank (store into buffer) 1 line

Y - yank (store into buffer) 1 line

p - put buffer content after current position

P - put buffer content before current position

[c|d|y]t - change/delete/yank up To char u - undo last command

U - ignore all changes in line since cursor moves into

current line

. - repeat last editing command

NOTE:

----

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(1) All above commands can be preceded by a number,

which indicates number of repetition.

E.g. 100G go to line number 100

2dd delete 2 lines

3yW yank 3 WORDS

(2) There are 10 unnamed buffers: "1 to "9

and 26 named buffers: "a to "z

Deleted lines are stored in to "1 to "9 as a stack implicitly.

Line/word/WORD(s) can be deleted/yanked into "a to "z explicitly.E.g. "a3Y yank 3 lines into "a

"bP put content of "b before current cursor position

EX line editing commands

------------------------

:q - quit

:q! - quit - no change of the file being edited

:w - write out the file being edited

:w! - overwrite the file being edited

:w fileName - write new file with name "fileName"

:w! fileName - overwrite the file "fileName"

:r fileName - read "fileName" in after current line

:e fileName - edit another file "fileName"

:vi fileName - edit another file "fileName" (same as above)

:e! fileName - edit another file - ignore change in current file

:!vi fileName - fork another process to edit another file "fileName"

:1 - goto 1-st line of file

:$ - goto last line of file

:1,$/pattern1/p - search for "pattern1" in file

globally & print it

:g/pattern1/p - search for "pattern1" in file

globally & print it

:g/pattern1/s//pattern3/ - search globally,

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replace first occurrence of "pattern1"

in ALL lines by "pattern3"

:g/pattern1/s//pattern3/g - search globally,

replace ALL occurrences of "pattern1"

in ALL lines by "pattern3"

:g/pattern1/s/pattern2/pattern3/g

- search globally,

in those lines with "pattern1",

replace ALL occurrences of "pattern2"

by "pattern3":set nu - set NUmbering

:set nonu - set NO NUmbering

:set ai - set auto-indent

:set ts=4 - set Tab-Stop = multiple of 4 char positions

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D Pico Command

Curser Movement

===============

^F move forward a character

^B move backwad a character

^P move to the Previous line.

^N move to the Next line.

Â move to the beginning of the current line.

Ê move to the End of the current line.

^V move forward a page of text.

^Y move backward a page of text.

^W Search for (where is) text, neglecting case.

Note: After ^W, press ^T to search for the line

^L Refresh the display.

Delete, Copy and Paste

======================

^D Delete the character at the cursor position.^^ Mark cursor position as beginning of selected text.

Note: Setting mark when already set unselects text.

^K Cut selected text (displayed in inverse characters)

Note: The selected texts boundary on the cursor side

ends at the left edge of the cursor. So, with

selected text to the left of the cursor, the

character under the cursor is not selected.

Or, cut the currrent line.

Û Uncut (paste) last cut text inserting it at the current cursor

position.

Other Command

=============

Î Insert a tab at the current cursor position.

^J Format (justify) the current paragraph.

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Note: paragraphs delimited by blank lines or indentation.

^T To invoke the spelling checker

^C Report current cursor position

^R Insert an external file at the current cursor position.

^O Output the current buffer to a file, saving it.

^X Exit pico, saving buffer.

^G Display Help

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Index, 29

>>, 30

, 27

., 27

.., 27

.forward, 19

acroread, 46

background job, 35

bg, 36

cat, 22

cd, 26

chfn, 40

chmod, 32

Absolute mode, 32

Symbolic mode, 32

cp, 24

credential, 10

du -k, 9

elm, 41

email forwarding, 19

fg, 36

file, 24

finger, 39

foreground job, 35

ghostview, 46

gimp, 45

gtar, 44

gunzip, 44

gv, 46

gzip, 44

head, 23

kill, 35

less, 22Linux, 5

lpq, 37

lpr, 37

lprm, 38

ls, 27

lynx, 42

Mac, 5

man, 47mkdir, 26

more, 22

mv, 23

passwd, 40

pico, 40

pine, 41

printquota, 38

ps, 34

quota -v, 9

rm, 21

rm -r (directory), 26

rmdir, 26

Secure shell, 12

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sftp, 41

SSH, 12

staroffice, 46

STDERR, 29

STDIN, 29

STDOUT, 29

tail, 23

talk, 39

tar, 44

tin, 42

top, 34, 35

touch, 21

UNIX, 5

UNIX account, 11

UNIX personal account, 6

unzip, 43

vi, 40vim, 40

w, 34

webster, 47

wget, 43

Windows account, 11

Windows profile, 6

write, 39

xv, 45

yppasswd, 40

zip, 43

zipinfo, 43

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