LECTURE 1, 2, 3

Introduction to computer architecture

Operation system tasks

Practical usage of UNIX/LINUX

Tomasz Zieliński

Department of Telecommunications AGH-UST

COMPUTER-BASED SYSTEM

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

µP equipment

+

system

+

application

computers

software

software

electronics

informatics

„how to do?”

computer science

processor

&

operating

systems (OS)

existing

computer

programming languages (PL) applications

architecture

hardware

OS

Unix

our

programs

know-how

C/C++

languages

algorithmics

using OS and PLs

COMPUTER = KINGDOM OF BITS (1)

voltage

„0”

„1”

< 0,7 V

> 2,7 V

NO

YES

sequences of bits:

!"""!!!"

- numbers:

fixed-point
floating -point
data for computations (input/output)
addresses

- characters:

alphanumerical (letters, digits, ...)
control (space, backspace, ...)

- processor instructions

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

bit
byte = 8 bits
word 16-bits
word 32-bits
word 64-bits

2

1

= 2

2*2*2*2*2*2*2*2=2

8

= 256

number of combinations
zeros and ones

2

16

= 65 536 = 64 KB

2

32

= 4 294 967 296 = 4 GB

2

64

COMPUTER = KINGDOM OF BITS –

NUMBERS

(2)

-----------------------------------------------------------------
!

"

!

!

!

"

"

!

!

graphically

-----------------------------------------------------------------
0 1 0 0 0 1 1 0

!

8 bits = 1 byte

-----------------------------------------------------------------
2

7

2

6

2

5

2

4

2

3

2

2

2

1

2

0

128 64

32

16

8 4 2 1 ! weights

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

64 + 4 + 2 = 70

!

result

Analogy to decimal positional number system, np. 123,45:

1

2

3,

4

5 = 1*100 + 2*10 + 3*1 + 4*0,1 + 5*0,01

---------------------------------------
10

2

10

1

10

0

10

−1

10

−2

100 10

1 0,1

0,01

COMPUTER = KINGDOM OF BITS –

NUMBERS

(3)

binary

decimal hexadecimal

EXAMPLE:

0000 0 0
0001 1 1 binary number
0010 2 2 %

0100 0110 = 0100 0110b

0011 3 3
0100 4 4 hexadecimal number
0101 5 5 0x

4 6 = 0x46 = 46h

0110 6 6
0111 7 7 decimal number
1000 8 8 70
1001 9 9
1010 10

A

1011 11

B

1100 12

C

1101 13

D

1110 14

E

1111 15

F

COMPUTER = KINGDOM OF BITS –

NUMBERS

(4)

0 1 0 0 0 1 1 0 = 0x46 = 70

actual

value

0 0 0 0 0 0 0 0 = 0x00 = 0

minimal

value on 8 bits

...

1 1 1 1 1 1 1 1 = 0xFF = 255

maximal

value on 8 bits

ASCII code (codes of alphanumerical characters)

0x41 =

65

=

A

0x20 space

0x42 = 66 = B

0x43 =

67

=

C

0x7B {

0x44 =

68

=

D

0x7D

}

...
0x5A

=

90

=

Z

0x2A *

...

0x2B +

0x61 =

97

=

a

0x62 = 98 = b

0x46 = F

0x63 = 99 = c
0x64 = 100 = d
...
0x7A = 122 = z

OxC9

OxBA

OxCC

OxC8

Table of ASCII codes (1): number

↔ character

Table of ASCII codes (2): number

↔ character

MICROPROCESSOR SYSTEMS IN WORK

µP =

microprocessor

X

A

B
Y

memory

address

PC

Arithmetic Logic Unit

ALU

control

move A,[X] ; A

← memory(adr in X)

move B,[Y] ; B

← memory(adr in Y)

add A, B ; A = A+B

move [X], A ; memory(adr=X)

← A

Asembler language

command
command
command

data
data
data

in/out
in/out

IR

data

IR = Instruction Register

PC = Program Counter

MEMORY USAGE IN COMPUTERS

Starting DOS operating system

Memory usage

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

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

START

Prog

BOOTSTRAP

COMMAND.COM

(from FD, HD, ..)

→ memory

File

CONFIG.SYS

→ values of system variables

What next?

User promts

to the operating system

Execution of commands from file

AUTOEXEC.BAT

BIOS

Memory

EROM (Read)

Memory

RAM (Read/Write)

Command.com

Free

operating

memory

for programs

Program A

Discs FD / HD

Program B

OS Commands

Stack

Interrupt progs

Graphics memory

Input/Out devices

CONFIGURATION FILES IN

DOS

OPERATING SYSTEM

CONFIG.SYS AUTOEXEC.BAT

FILES=

30

BUFFERS=

50

STACKS=

9,256

SHELL=

c:\command.com /E:1024 /P

LASTDRIVE=

H

DEVICE=

C:\DOS\SETVER.EXE

DEVICE=

C:\DOS\HIMEM.SYS

DEVICE=

C:\DOS\RAMDRIVE.SYS 8096 512 /E

DOS=

HIGH

REM

DOS=HIGH,UMB

@ECHO

OFF

PROMPT

$p$g

PATH

C:\;C:\DOS;C:\NC;C:\EDIT;

APPEND

C:\EDIT

SET

LIB=C:\FORT\LIB

SET

INCLUDE=C:\FORT\INCLUDE

SET

TMP=E:\

REM

C:\WINDOWS\SMARTDRV.EXE

CLS
TYPE

WELCOME.TXT

PAUSE
CLS

mode mono
mode con rate=32 delay=1
c:\mouse\mouse.com /R4
c:
nc

COMPUTER INTERFACE WITH INPUT/OUTPUT DEVICES

µP

Memory

for interfacing

with input/output

devices

Command

Status

Data

OUT

Data

IN

µC

Data buffers

Hard disc

step motor
magnetic heads
cylinders/platters

tracks/sectors/
clasters

CONNECTING COMPUTERS

Memory

In / Out

µP 1

In / Out

µP 2

Memory

Terminal PC
Windows

PuTTY
program

Server
Unix

pico - editor
gcc - compiler C

EXAMPLE

Example of programming in computer network:

PuTTY

student.uci.agh.edu.pl

connecting

with UCI-AGH server

login: ?

registration:

student account on the server

password:

?

password

for this account

touch

prog1.c

creation

of EMPTY file: prog1.c

pico

prog1.c

editing

this file:

CTRL+O = write, CTRL+X = exit

gcc

prog1.c

compiling and linking

file prog1.c

to

program prog1.out

FILES AND DIRECTORIES IN DIFFERENT OPERATING SYSTEMS

program 1

program 2

zbiór 1

zbiór 2

directory A

directory B

MAIN

DIRECTORY

program 3

prog1.exe

prog2.com

prog3.bat

zb1.dat, zb1.txt

zb2.doc, zb2.par

DOS

Windows

program 4

program 5

file 3

directory C

program 6

file 4

file 5

directory D

directory E

prog1

prog2

prog3

zb1

zb2

Unix

Linux

file
attributes
specify
file
type

/home

/home/prog1

~/prog2

~/zb1

~/zb2

~/prog3

/home/dirB/prog6

/home/dirB/zb4

/home/dirB/zb5

C:\

C:\prog1.exe

C:\dirA\prog4.exe

actual
directory

UNIX

− OPERATIONS ON DIRECTORIES AND DISC FILES

======================================EXAMPLE OF USAGE========

pwd

–

present work directory

pwd

ls

–

list (files, directories)

ls

/home, ls /home/dirA

mkdir

–

make directory

mkdir

/home/dirX, mkdir ~/dirY

rmdir

–

remove directory

rmdir

/home/dirX, rmdir ~/dirY

cd

–

change directory

cd

/home, cd /home/dirA, cd ../..

touch

–

create empty file

touch

/home/dirA/dirC/prog

rm

–

remove file(s)

rm

/home/dirA/dirC/prog

cp

–

copy file(s)

cp

file1 file2, cp *.c?? *.cpp

mv

–

move file(s)

mv

~/file1 ~/dirA/file2

cat

–

concatenate file(s)

cat

file1 file2 > file3

chmod

.. –

change mode (of file)

chmod

a=

rwx

file

(read, write, exec)

man

–

manual (opis)

man

chmod

(Q = quit!!!)

================================================================
~, .

– present directory

* -

any sequence of characters

..

– directory one level up

? –

any character

../..

– directory two levels up

UNIX

− PROGRAM EDITION AND COMPILATION

touch

– file creator

gcc

– general C compiler

pico

– editor

g++

– general C++ compiler

gdb

– general debugger

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

touch

prog1.c create

an

empty

file

prog1.c

(EMPTY!)

pico

prog1.c CTRL+O

=

write

CTRL+X = exit

gcc

prog1.c compiling

and

linking

to

prog1.out

gcc

prog1.c –o

prog1

compiling

and

linking

to

prog1

gcc

–c

prog1.c only

compiling

to

prog1.o

gcc

–l prog1.o prog2.o –o prog12

only linking progs prog1.o prog2.o
to

prog12

More about UNIX/LINUX operating system

and its usage

GENERAL CHARACTERISTIC OF

UNIX/LINUX OS

UNIX history at a glance:

1969

– first

Unix

system written in

assembler

in Bell Labs AT&T

1973 – rewriting

Unix

code in

C language

by D. Ritchie and B. Kernighan

1980-1990 – new technologies:

TCP/IP (

Transmission Control Protocol / Internet Protocol

),

GNU OS (

GNU is Not Unix

),

POSIX (

Portable Operating System Interface

)

1991

– Linus Torvalds, Finnish student, wrote kernel of

Linux

operating system

After – development of many Unix “clones”, Open Source community

Main UNIX features:

– multi-tasking and multi-user
– system scalability
– system stability
– code portability
– accessibility of free software (Linux)

Members of UNIX family:

SCO XENIX FreeBSD

SGI IRIX

NetBSD

different Linux distributions:

Knoppix, Ubuntu, ...

Linux

FreeBSD

LAYERS OF

UNIX/LINUX

• System Unix/Linux is built from layers.
• System KERNEL represents its main element.
• It is surrounded by layers ensuring communication with users and different

devices, including input/output ones.

Shells, commands, applications

User

User interface

Interface to libraries

Interface to system calls

Interface to hardware layer

System KERNEL:

controlling processes, resources, …

Hardware layer:

CPU, memory, discs, drivers, …

GNU C library (glibc)

programs

compilers

Graphical presentation

of Unix/Linux layers

SHELLS

OF

UNIX/LINUX

OPERATING SYSTEMS

Shell

represents an interface between a user and the operating system.

Main tasks:





Standard

UNIX

shells:

Their

newer

alternatives:

♦

In LINUX systems

bash shell

is very popular.

♦

It has all commands of

sh shell + additional functions

(syntax supplements,

command history and many new facilities).

♦

Shell can be changed using command

$ chsh

– user commands interpretation and execution
– interface between a user and system KERNEL
– automation of different actions by means of scripts (files with OS commands)

Bourne shell (sh)

bash

(Bourne-Again Shell)

Korn shell (ksh)

zsh (Z Shell)

C shell (csh)

tcsh

(TC-Shell)

COMPARISON OF TWO SHELLS:

BASH

AND

TCSH

BASH:

• the most

popular

shell in Unix systems

• easy in use

•

compatible

with the shell

sh

•

put together features

of two shells: Korn (

ksh

) and C (

csh

)

• has specific variables

TCSH:

• second very popular shell

• extended version of the shell C (

csh

)

• its script syntax is very similar to C language programming

• includes mechanism of transcription correction

• has specific variables

Main differences concern script files.

SYSTEM COMMANDS (1)

General syntax:

encouraging mark $ command_name [options, arguments, …]

Letter options are precede with mark „

-

”, word options – with mark „

--

”

Every command has usually its help: „

-h

” or „

--help

”, e.g.

anycommand -h

Additional information is given by manual:

$ man anycommand

Loging and changing password:

$

login

[

account

]

–

Create a new working session

with the system.

Parameter

account

must be an existing user (or administrator) account. User is

asked for a password if the account exists.

$

passwd

[

param

]

–

Change a user password

. In no parameters are given,

password of actually logged user is changed.

$

logout, exit

–

Finish this working session

(Ctrl+D).

Przykład zakładania konta użytkownika:

$

useradd

account_name

-

create an account „account_name”

$

passwd

account_name

-

create a password for this account

$

login

account_name

-

login using the created account

SYSTEM COMMANDS (2)

Display

of basic information:

$

who

[options] [file|arg1|arg2]

-

show who is actually logged-in

$

uname

[options]

...

-

show system information

$

w

–

show actually working users and their processes

Examples:

Testing network connections:

$

ping

[options] [host_address] –

test connection between computers

$

traceroute

[host_address] -

trace packets route in the network

Examples:

$

who

, $

w

-

display user who are logged-in

$

uname

–o -v

-

display OS name (-o) and kernel version (-v)

$

ping

–c 3 address -

send 3 echo claims (to the given IP address)

$

traceroute

address - show trace route of the given IP address

REMOTE ACCESS

Commands related to remote access:

$

telnet

[host] -

connect to remote host using

telnet

remote session.

It allows to work on remote server like on your own
computer (using local network or Internet).

$

rlogin

[options] [host]

–

login

on remote computer

$

rsh

[options][host] [command] –

execute

command on remote host

$

ssh

[options][host] [command] –

as above, but

with data encryption

A


Examples:

$

telnet

host1

-

connect

to remote host1

$

rlogin

host1

-

login

on remote host1

$

rsh

host1 df

-

check

free space on host1

$

ssh

host1 df

-

as above, but with encyption (security) !

At present only the last command

ssh

(secure shell)

is used.

The transmission is

encrypted (coded, scrambled)

and therefore more safety.

USING MANUALS

Most commands contain

help information

of their usage putted in

man

(manual)

instruction. In general, one can get information using the following commands:

$

man

[-options] subject

$

info

subject

$

whatis

command

$

apropos

[searched_word ... ]

Sometimes in manual there are available a few pages of description for one
command, for example printf(3). We can access these pages as follows:

$ man 3 printf

During manuals reading:

<enter>

– new line

<spacja>

– new page

<q>

– quit

Examples:

$

man

man

$

info

info

$

man

ls

$

info

vi

$

man

ftp

$

info

grep

$

whatis

ls

$

apropos

list

whatis

find and display short command

description

whereis

where is localized command or its

help script

apropos

search for specific strings in manual

description

TREE STRUCTURE OF DIRECTORIES

/bin

Commands and programs available for users

/sbin,

System and administrator’s programs

/dev

Special files, representing different devices

/etc

System

configuration

files

/tmp Temporary

files

/lib

System libraries, header files

/proc

Special directory, system information

/lost+found Recovered files after checking of file system

integrity

/usr/local

Additional system software

/var

Varying system scripts (logins, queues, etc.)

/home

Directory for user accounts (exception: /root)

MANAGEMENT OF FILE SYSTEM

Unix command

Description

MS DOS

ls [options] [files]

Display directory content

$ ls -al /home

> dir

cd [dir_name]

Change directory

$ cd .. $ cd ~

> cd

mkdir [dir_name]
rmdir [dir_name]

Make empty/ remove directory

$ mkdir my_dir
$ rmdir my_dir

> md
> rd

cp [file1] [file2]
mv [file1] [file2]

Copy/move file

$ cp src dest

> copy, > move

rm [file]

Remove file

$ rm file_name

> del

rm –rf [dir_name]

Remove directory with files

$ rm -rf my_dir

> deltree

touch [file_name]

Create new, empty file

$ touch file1

-

ln [options] [s] [d]

Create symbolic link

$ ln –s src dest

-

CATEGORIES OF USERS AND ACCESS RIGHTS

Each

file and directory

in Unix/Linux system has an owner who can performs

different operations on it, specified by

access rights

.

User categories:






Three types of access rights:

Kod

File

Directory

r

(read)

Right to read

Right to read directory content

w

(write)

Right to write (change)

Right to change directory content

x

(execute)

Right to execute

Right to entrance to directory

File attributes can be displayed

using command:

$

ls

–l file_name

a

ll

all users

u

ser

user, file owner

g

roup groups of the file owner

o

ther other users

FILE ATTRIBUTES

(ownership, display)

execute 1/0

write 1/0

read....…1/0

-rwxrw-r-- 1 user group ... file_name

g

o

u

u

ser

g

roup

o

ther

type

-

ordinary

file

d

directory = list of files

l

symbolic link

c

urządzenie znakowe (np. modem)

b

block device (e.g. disc)

p

named

pipe

s

socket

Symbolic link

Special file type that is pointing to
other file or directory.

Link can be

„soft” or „hard”.

In Microsoft Windows similar role
plays shortcut.

number of
symbolic links

ADMINISTRATION OF ACCESS RIGHTS

Commands for changing (giving) access rights:

chmod

–

change access rights

to specified file

chown

–

change file owner

chgrp

–

change file attachment to group

Method 1 SYMBOLIC:

$ chmod [who] operator [permission][,...] file_name

Mehod 2 OCTAL:

$ chmod octal_code file_name

operator:

+ add

permission

– cancel permission

= change

permission

who:

a all

u user
g group
o others

permission

for:

r read
w write

x execute

octal_code – sum of octal codes for different groups:
user r=400

w=200

x=100

group r=040

w=020

x=010

others r=004

w=002

x=001

Examples:

Results:

$ chmod 777 plik1 -rwxrwxrwx

$ chmod 641 plik2 -rw-r----x
$ chmod 555 plik3 –r-xr-xr-x

Examples:

$ chmod a+w plik1
$ chmod u-w plik2
$ chmod u=rw,o=r plik3

ARCHIVES OF FILES

Traditionally Unix system has a command for administration of archives.
Since initially it was used for data storage on magnetic tapes
it was given the name

tar

(Tape Archive)

.

Syntax: $ tar

[

-options

]

[…]

Examples:

Create file

name.tar

:

$ tar -cvf

name.tar

file1 file2

Add file to existing archives: $ tar -rvf name.tar file_added
Extract files from archives:

$ tar -xvf name.tar

Write out archives content:

$ tar -tf name.tar

-c

-

create

a new archives

-r

- add file to the archives on its end

-u

- write new or modified files to the archives (

update

)

-x

-

extract

file from the archives

-f

name

- give name of the archives

-t

- write out the archives content

-v

- inform about performed operations on the archives (

verbose

)

COMPRESSION OF FILES

Commands:

gzip

,

bzip2

Syntax:

$

gzip

[-options][file]

$

bzip2

[-options][file]

Examples:

Options for

bzip2

command:

-z =

compression

–d =

decompression

Command

tar

can also do compression

when the following additional options are used:

-z

compression/decompression of archives using

gzip

-j

compression/decompression of archives using

bzip2

Example:

$

tar

-c

z

vf name.tar file1 file2

$

gzip

name

-

compress file

name

$

gzip

–d name

-

decompress file

name

$

gzi

p –r *

-

compress all files in actual directory and all subdirectories

$

gzip

–dr *

-

decompress all files in actual directory and all subdirectories

separate
resultant
files

STREAMS AND PIPES

Stream types:

Operators for

stream redirection

:

Example: $ date > date_time - write

to file

date_time

date and time printing

Pipes

– make available sending data from one command to the other one.

Pipe operator character =

“|”

(vertical line, Shift+\)

Example: $ ls –l /dev | more

− paging result of ls –l /dev

1) Input

0, keyboard is default, stdin

2) Output

1, screen is default, stdout

3) Error

2, screen is default, stderr

>

output stream redirection with overwriting (e.g. to file)

>>

output stream redirection with addition to the end

<

input stream redirection with overwriting (e.g. to buffer)

<<

input stream redirection with addition to the end

CONTENT PROCESSING

Commands for file processing:

$

cat

[parameters] [file]

Concatenate files and show their
contents

Examples:

cat

file1 file2 > file3

$

cut

[parameters] [file]

Cut interesting fragment of text from
given file and display it on the screen

Some options:

-c list

– character

e.g. –c1-5 – first 5 chars in each line

-b list

–

byte e.g. –b1-5 – first 5 bytes in each line

-d delim

–

special character (default tab) e.g. -d :

Example:

cut

–c 4-10 file1

–

show chars 4-10 in each line

cut

-d : -f 5- file1

–

from 5-th word in each line, delim = :

COMMAND / LANGUAGE

AWK

awk

is used for scripts (text files) processing.

AWK

= „

A

ho,

W

einberger, &

K

ernighan” (author’s names)

As a command

it can perform simple text operations.

As a language

it is a very powerful tool for performing complex editorial operations.

Program written in AWK consists of blocks having the following syntax:

Simple programs can be executed directly from command line:

Example of simple using:

condition { commands }

awk

‘condition {command}’ script

awk

‘/user/ {print}’ /etc/passwd

– display lines of script /etc/passwd,

containing regular expression user (that has to be between two characters “/”)

SEARCHING

Command

find

– searching in complex structures of directories

Syntax: $

find

where criterion action

Program

grep

– (

general regular expression print

)

very complex program that displays / prints all lines (in specified files) that fit (or not)
to the given pattern.

Syntax: $

grep

[options] regular_expression [files]

where

where to start searching (default: actual directory)

cryterion

searching criterion (default: all files)

action

what to do with the result of searching (default: -print)

Examples:

$

find

/etc –name passwd

$

find

/home –name *.c

Examples:
$

grep

‘int’ /home

print lines having pattern ‘int’

$

grep

–v

‘int’ /home

print lines not having pattern ‘int’

$

grep

–c

‘int’ /home

print file names and number of lines having pattern

‘int’

Other options:
–name xyz
–user xyz
–group xyz

REGULAR EXPRESSIONS (1)

Regular expressions (used also in Perl, POSIX) represent a tool for looking for
reference character patterns and filtering information in script files.

They are used together with specific commands, e.g.

find

i

grep

Look examples above:

*.c

in

find

and

'int'

in

grep

Operator

Description

Example

Fitting YES Fitting NO

|

Operator OR

‘a|b|c’

‘abc’,‘bc’

‘de’

.

Any single character

‘plik.a’

‘plik1a’

‘plika’

^

Beginning of line

‘^plik’

‘plik1a’

‘plikaa12’

‘replika’

$

End of line

‘plik$’

‘nowyplik’

‘plik1’

*

Zero or more appearance
of last character

‘plik.*a’

‘plika’

‘plik

xx

a’

‘plik

xy

za’

‘plikb’

\

Next character is not treated
as a special one

‘plik\.’

‘plik.24’

‘plik2’

REGULAR EXPRESSIONS (2)

Operator

Description

Example

Fitting Yes Fitting No

[...]

Any character (only one)
from the given list

‘[Pp]lik’

‘Plik’
‘plik’

‘klik’

[^...]

Any character
NOT from the given list

‘[^Pp]lik’

‘klik’

‘plik’

[\b]

String on the word borders

‘\bplik’

‘pliknew’ ‘newplika’

\(...\)

Definition of sub-expression

‘\(plik\)’

‘plik’

-

[\n]

Refering to the n-th sub-expression
(n from 1 to 9)

\(plik\).*\1

plik

x

plik

plik

xy

plik

plikxklik

\< ..\>

Refering to the whole word

‘\<plik\>’ ‘plik’ ‘pliki’

TEXT EDITOR

Vi

(M)

The most known text editor in Unix, developed by Billa Joya, Sun Microsystems.
Admired and hated!

Working modes:

Command Mode
Input Mode

Switch to Command Mode:

ESC

Switch to Input Mode:

i, I, a, A, r, R, o, O
(insert, append, replace, new line)

Start editor:

$ vi file_name

Stop editor and write to file:

ZZ

– write to file and return to console

:q! – quit without saving to file
:wq – quit with saving to file

Remove text (x chars,dd lines):

x, X, dd, [n]x, [n]X

(remove n chars)

Moving in edition window:

h, j, k, l

(left, down, up, right)

Ctrl-f, Ctrl-b

(screen – for/ backwards)

Ctrl-u, Ctrl-d

(half-screen – up, down)

Copy text:

[n]yw

(copy to buffer n words)

[n]yy

(copy to buffer n lines)

p, P

(paste from buffer before/After)

Search text:
:/ref, :?ref,

(search down or up)

n, N

(repeat last search)

Literature:
$ man vi

$ vimtutor

(short course on vi(M))

OTHER EDITORS (PICO, NANO, JOE …)

Editors more user-friendly, better for beginners.
PICO is a part of packet PINE used for administration of electronic mail in Unix.

Main

commands:

Moving

in

editor:

Marking,

cuting,

pasting:

Suggested

literature:

Ctrl-^ – go to marking mode

$ man pico

Ctrl-k – cut the marked fragment

$ man nano

Ctrl-u – paste the marked fragment

$ info nano

Ctrl-g – help
Ctrl-o –

write to file

Ctrl-x –

write to file and quit

Ctrl-t – check spelling
Ctrl-j – text justification
Ctrl-w – search in file

Ctrl-f – move forwards 1 character
Ctrl-b – move backwards 1 character
Ctrl-p – move up 1 line
Ctrl-n – move down 1 line
Ctrl-a – jump to the beginning of line
Ctrl-e – jump to the end of line

SPECIAL FILES (1)

File

/etc/passwd

In ASCII format, containing list of users and their passwords.

Structure of user record:

login_name

- user name in the system

password

- encoded password of the user

UID

- user identifier (number)

GID

- group identifier (number)

name_surname

- user name

directory

- user home directory ($HOME)

shell -

user

shell

(program run after user login)

login_name:password:UID:GID:name_surname:directory:shell

tzielin:x:30068:555:Tomasz Zielinski:/home/tzielin:/bin/bash

SPECIAL FILES (2)

File

/etc/group

In ASCII format, defining groups of users

Strukture of group records:

group_name:password:GID:user_list

group_name

- group name

password

- encoded (if no password is given, it is not required)

GID -

group

identifier

(number)

user_list

- user names belonging to the group

EXAMPLE: adm:x:4:root,adm,daemon

SPECIAL FILES (3)

Selected important start-up scripts:






Selected configuration scripts:






Local shell configuration scripts (

IMPORTANT FOR THE USER

):

/etc/inittab -

using during system start-up

/etc/rc

-

main configuration script (sometimes in /etc/rc.d)

/etc/rc.config

-

configuration script used by /etc/rc for pars initialization

/etc/rc.local -

used for local administration

/etc/fstab

-

file system, installation of disc

/etc/profile

-

configuration file for shells

sh/bash

/etc/csh.login

-

configuration file for shells

csh/tcsh

/etc/shadow

-

encrypted

passwords

of user accounts

~/.profile -

for

sh

~/.csh

rc

-

for

csh

~/.tcsh

rc

-

for

tcsh

~/.bash

rc

-

for

bash

SCRIPTS

Content of the easiest script

for the bash shell (script1.sh):

Script

= uncompiled executable text file, consisting of system commands

and

some control/logic “glue” (instructions, loops, etc.).

Executed by interpreter translating script code (program, sequence of
commands) to machine language understanding by processor.

# Shell type to be executed (# denotes start of remark)
#!/bin/bash
echo „My first script”

# Display text in quotation-marks

Written script should be executable (giving him the right to execution):
$ chmod u+x script1.sh

Execution (running) of script being in actual directory:
$ ./script1.sh

ENVIRONMENTAL / SYSTEM VARIABLES (1)

Environmental / system variables

– names of objects containing information used

by one or many programs in operating system.

There are 4 variable types:

Local variables

Define shell configuration, they are visible only for the
shell for which they were defined

$ set •

read values of all local variables

$ echo $variable •

read value of the selected variable

$ export -n

variable=new_value

•

change variable value

Example:

PS1=

[\u@\h \W]\$

– set encouraging mark

Global variables

They are visible from any shell

$ export

variable=new_value

•

change variable value

Example:

EDITOR=vi

-

name of the default text editor

ENVIRONMENTAL / SYSTEM VARIABLES (2)

Special variables

They are defined by the system and user can not
change their values.

Examples:

$#

• number of parameters sent to program

#?

• exit code of command/program executed in the shell

$0

• name of executed program

$1,$2,...

• consecutive parameters sent to program/command

Program variables

Defined by user in shell scipts

variable=value

• definition and initialization of program variable

$ echo $variable

• read value of selected variable

Examples of variables:

x=123

- definition on number variable

name=”Tomek”

- definition of string variable

CONDITIONAL INSTRUCTIONS (1)

Instruction

if

:

$x

–

value of variable

x

Condition

can include different comparisons and tests:

Example:

#!/bin/bash
echo "Give login:"
read login

if

[ "$login" != "mis" ]

then

echo 'Access denied'

else

echo 'Welcome in the system'

fi

if

condition

then

instructions1

else

instructions2

fi

•

numbers

:

-gt

(greater),

-lt

(lower),

-ge

(greater or equal),

-le

(lower or equal),

-eq

(equal),

-ne

•

text

:

-z

(empty?),

-n

(string value),

=

,

!=

(different),

Str

(null string?)

•

logical

:

-a

( && ) (logical and),

-o

( || ) (logical or),

!

(logical not)

•

files

:

-f

(file existence),

-s

,

-r

,

-w

,

-x

,

-d

(folder),

-h

(symbolic link),

-c

CONDITIONAL INSTRUCTIONS (2)

Instruction

case

:

Example:

#!/bin/bash
echo "Give number of a week day"
read d

case

"$d"

in

"1") echo "Monday" ;;
"2") echo "Tuesday" ;;
"3") echo "Wednesday" ;;
"4") echo "Thursday" ;;
"5") echo "Friday" ;;
"6") echo "Saturday" ;;
"7") echo "Sunday" ;;
*) echo "No number was given"

esac

case

variable

in

"tamplate1") command1 ;;

"tamplate2") command2 ;;

"tamplate3") command3 ;;

*) default_command

esac

LOOPS (1)

Loop

for

:

Loop

select

:

Example:

change file names, capital letters --> small

#!/bin/bash

for

name

in

*

do

mv

$name ‘echo $name |

tr

\

'[A-Z]''[a-z]'‘

done

Example:
#!/bin/bash
echo "What are you choosing?"

select

y

in

X Y Quit

do

case

$y

in

"X")

echo "X is chosen" ;;

"Y")

echo "Y is chosen" ;;

"Quit") exit ;;
*)

echo "Nothing is chosen"

esac

break

# Break the do loop

done

for

variable

in

list

do

instructions

done

select

variable

in

list

do

instructions

done

continue in next line

LOOPS (2)

Loop

while

:

Loop

until

:

Example:

#!/bin/bash
x=1;

while

[ $x -le 10 ]

do

echo "This is display number: $x"
x=$[x + 1]

done

Example

:

#!/bin/bash
x=1;

until

[ $x -ge 10 ]

do

echo "This is display number:: $x"
x=$[x + 1]

done

while

condition

do

instructions

done

until

condition

do

instructions

done

Configuration scripts for shells Bash i Csh/Tcsh:

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

Script profile for Slackware

(the oldest Linux distribution,

by many persons treated as the only genuine / authentic):
===========================================

# /etc/profile: This file contains system-wide defaults
# used by all Bourne (and related) shells.

# Set the values for some environment variables:

export MINICOM="-c on"
export MANPATH=/usr/local/man:/usr/man
export HOSTNAME="`cat /etc/HOSTNAME`"
export LESSOPEN="|lesspipe.sh %s"
export LESS="-M"

# If the user doesn't have a .inputrc, use the one in /etc.

if [ ! -r "$HOME/.inputrc" ]; then
export INPUTRC=/etc/inputrc
fi

# Set the default system $PATH:

PATH="/usr/local/bin:/usr/bin:/bin:/usr/games"

# For root users, ensure that /usr/local/sbin, /usr/sbin, and /sbin
# are in the $PATH.
# Some means of connection don't add these by default
# (sshd comes to mind).

if [ "`id -u`" = "0" ]; then
echo $PATH | grep /usr/local/sbin 1> /dev/null 2> /dev/null
if [ ! $? = 0 ]; then
PATH=/usr/local/sbin:/usr/sbin:/sbin:$PATH
fi
fi

# I had problems with the backspace key using 'eval tset'
# instead of 'TERM=',
# but you might want to try it anyway instead of the section below it.
# I think with the right /etc/termcap it would work.
# eval `tset -sQ "$TERM"`

# Set TERM to linux for unknown type or unset variable:

if [ "$TERM" = "" -o "$TERM" = "unknown" ]; then
TERM=linux
fi

# Set ksh93 visual editing mode:

if [ "$SHELL" = "/bin/ksh" ]; then
VISUAL=emacs
# VISUAL=gmacs
# VISUAL=vi
fi

# Set a default shell prompt:
#PS1='`hostname`:`pwd`# '

if [ "$SHELL" = "/bin/pdksh" ]; then
PS1='! $ '
elif [ "$SHELL" = "/bin/ksh" ]; then
PS1='! ${PWD/#$HOME/~}$ '
elif [ "$SHELL" = "/bin/zsh" ]; then
PS1='%n@%m:%~%# '
elif [ "$SHELL" = "/bin/ash" ]; then
PS1='$ '
else
PS1='\u@\h:\w\$ '
fi
PS2='> '
export PATH DISPLAY LESS TERM PS1 PS2

# Default umask. A umask of 022 prevents new files
# from being created group and world writable.

umask 022

# Notify user of incoming mail. This can be overridden in the user's
# local startup file (~/.bash.login or whatever, depending on the shell)

if [ -x /usr/bin/biff ]; then
biff y 2> /dev/null
fi

# Append any additional sh scripts found in /etc/profile.d/:

for profile_script in /etc/profile.d/*.sh ; do
if [ -x $profile_script ]; then
. $profile_script
fi
done
unset profile_script

# For non-root users, add the current directory to the search path:

if [ ! "`id -u`" = "0" ]; then
PATH="$PATH:."
fi

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

Script csh.login:

(configuration of shells csh i tcsh)

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

# /etc/csh.login: This file contains login defaults used by csh and tcsh.

# Set up some environment variables:

if ($?prompt) then
umask

022

set cdpath = ( /var/spool )

set

notify

set history = 100
setenv MANPATH /usr/local/man:/usr/man

setenv MINICOM "-c on"

setenv HOSTNAME "`cat /etc/HOSTNAME`"

setenv LESS "-M"

setenv LESSOPEN "|lesspipe.sh %s"

set path = ( /usr/local/bin /usr/bin /bin /usr/games )

endif

# If the user doesn't have a .inputrc, use the one in /etc.

if (! -r "$HOME/.inputrc") then

setenv INPUTRC /etc/inputrc

endif

# I had problems with the backspace key installed by 'tset',
# but you might want to try it anyway instead of the section below it.
# I think with the right /etc/termcap it would work.
# eval `tset -sQ "$term"`

# Set TERM to linux for unknown type or unset variable:

if ! $?TERM setenv TERM linux
if ("$TERM" == "") setenv TERM linux
if ("$TERM" == "unknown") setenv TERM linux

# Set default POSIX locale:

setenv LC_ALL POSIX

# Set the default shell prompt:

set prompt = "%n@%m:%~%# "

# Notify user of incoming mail. This can be overridden in the user's
# local startup file (~/.login)

biff y >& /dev/null

# Set an empty MANPATH if none exists
# (this prevents some profile.d scripts
# from exiting from trying to access an unset variable):

if ! $?MANPATH setenv MANPATH ""

# Append any additional csh scripts found in /etc/profile.d/:

[ -d /etc/profile.d ]
if ($status == 0) then
set nonomatch
foreach file ( /etc/profile.d/*.csh )
[ -x $file ]
if ($status == 0) then
source $file
endif
end
unset file nonomatch
endif

# For non-root users, add the current directory to the search path:

if (! "$uid" == "0") set path = ( $path . )

Command syntax in scripts of shells: BASH and TCSH

bash

tcsh

for

variable

in

list

do

instruction

done

foreach

variable (

list

)

instruction

end

while

expression

do

instruction

done

while

(expression)

instruction

end

if

[ expression ];

then

instruction

elif

[ expression ];

then

instruction

else

instruction

fi

if

(expression)

then

instruction

else if

(expression)

then

instruction

endif

case

variable

in

value1 | value2)
instruction;;
value3 | value4)
instruction;;
*) instruction;;

esac

switch

(variable)

case

value1 | value2

:

instruction

breaksw

case

value3 | value4

:

instruction

breaksw

default:

instruction

breaksw

endsw