UNIX Tutorial || Chapter Two

2.1 Copying Files

cp (copy)

cp file1 file2 is the command which makes a copy of file1 in the current working directory and calls it file2

What we are going to do now, is to take a file stored in an open access area of the file system, and use the cp command to copy it to your unixstuff directory.

First, cd to your unixstuff directory.

% cd ~/unixstuff

Then at the UNIX prompt, type,

% cp /vol/examples/tutorial/science.txt .

Note: Don’t forget the dot . at the end. Remember, in UNIX, the dot means the current directory.

The above command means copy the file science.txt to the current directory, keeping the name the same.

(Note: The directory /vol/examples/tutorial/ is an area to which everyone in the school has read and copy access. If you are from outside the University, you can grab a copy of the file here. Use ‘File/Save As..’ from the menu bar to save it into your unixstuffdirectory.)

Exercise 2a

Create a backup of your science.txt file by copying it to a file called science.bak

2.2 Moving files

mv (move)

mv file1 file2 moves (or renames) file1 to file2

To move a file from one place to another, use the mv command. This has the effect of moving rather than copying the file, so you end up with only one file rather than two.

It can also be used to rename a file, by moving the file to the same directory, but giving it a different name.

We are now going to move the file science.bak to your backup directory.

First, change directories to your unixstuff directory (can you remember how?). Then, inside the unixstuff directory, type

% mv science.bak backups/.

Type ls and ls backups to see if it has worked.

2.3 Removing files and directories

rm (remove), rmdir (remove directory)

To delete (remove) a file, use the rm command. As an example, we are going to create a copy of the science.txt file then delete it.

Inside your unixstuff directory, type

% cp science.txt tempfile.txt
% ls
% rm tempfile.txt
% ls

You can use the rmdir command to remove a directory (make sure it is empty first). Try to remove the backups directory. You will not be able to since UNIX will not let you remove a non-empty directory.

Exercise 2b

Create a directory called tempstuff using mkdir , then remove it using the rmdir command.

2.4 Displaying the contents of a file on the screen

clear (clear screen)

Before you start the next section, you may like to clear the terminal window of the previous commands so the output of the following commands can be clearly understood.

At the prompt, type

% clear

This will clear all text and leave you with the % prompt at the top of the window.

 

cat (concatenate)

The command cat can be used to display the contents of a file on the screen. Type:

% cat science.txt

As you can see, the file is longer than than the size of the window, so it scrolls past making it unreadable.

 

less

The command less writes the contents of a file onto the screen a page at a time. Type

% less science.txt

Press the [space-bar] if you want to see another page, and type [q] if you want to quit reading. As you can see, less is used in preference to cat for long files.

 

head

The head command writes the first ten lines of a file to the screen.

First clear the screen then type

% head science.txt

Then type

% head -5 science.txt

What difference did the -5 do to the head command?

 

tail

The tail command writes the last ten lines of a file to the screen.

Clear the screen and type

% tail science.txt

Q. How can you view the last 15 lines of the file?

 

2.5 Searching the contents of a file

Simple searching using less

Using less, you can search though a text file for a keyword (pattern). For example, to search through science.txt for the word ‘science’, type

% less science.txt

then, still in less, type a forward slash [/] followed by the word to search

/science

As you can see, less finds and highlights the keyword. Type [n] to search for the next occurrence of the word.

 

grep (don’t ask why it is called grep)

grep is one of many standard UNIX utilities. It searches files for specified words or patterns. First clear the screen, then type

% grep science science.txt

As you can see, grep has printed out each line containg the word science.

Or has it ????

Try typing

% grep Science science.txt

The grep command is case sensitive; it distinguishes between Science and science.

To ignore upper/lower case distinctions, use the -i option, i.e. type

% grep -i science science.txt

To search for a phrase or pattern, you must enclose it in single quotes (the apostrophe symbol). For example to search for spinning top, type

% grep -i ‘spinning top’ science.txt

Some of the other options of grep are:

-v display those lines that do NOT match
-n precede each matching line with the line number
-c print only the total count of matched lines

Try some of them and see the different results. Don’t forget, you can use more than one option at a time. For example, the number of lines without the words science or Science is

% grep -ivc science science.txt

 

wc (word count)

A handy little utility is the wc command, short for word count. To do a word count on science.txt, type

% wc -w science.txt

To find out how many lines the file has, type

% wc -l science.txt

Summary

Command	Meaning
cp file1 file2	copy file1 and call it file2
mv file1 file2	move or rename file1 to file2
rm file	remove a file
rmdir directory	remove a directory
cat file	display a file
less file	display a file a page at a time
head file	display the first few lines of a file
tail file	display the last few lines of a file
grep ‘keyword’ file	search a file for keywords
wc file	count number of lines/words/characters in file

GSM ARCHITECTURE

Information on GSM Architecture

A GSM network consists of the following components:

Mobile station:

The GSM mobile station (or mobile phone) communicates with other parts of the system through the base-station system.

GSM Base station system (BSS):

Base transceiver station (BTS). The base transceiver station (BTS) handles the radio interface to the mobile station. The base transceiver station is the radio equipment (transceivers and antennas)

Base station controller (BSC):

The BSC provides the control functions and physical links between the MSC and BTS. It provides functions such as handover, cell configuration data and control of RF power levels in base transceiver stations. A number of BSCs are served by a MSC.

 

Image via Wikipedia

GSM Switching System:

Mobile services switching center (MSC). The MSC performs the telephony switching functions of the system. It also performs such functions as toll ticketing, network interfacing, common channel signalling, and others.

Home location register (HLR):

The HLR database is used for storage and management of subscriptions. The home location register stores permanent data about subscribers, including a subscriber’s service profile, location information, and activity status.

Visitor location register (VLR):

The VLR database contains temporary information about subscribers that is needed by the mobile services switching center (MSC) in order to service visiting subscribers. When a mobile station roams into a new mobile services switching center (MSC) area, the visitor location register (VLR) connected to that MSC will request data about the mobile station from the HLR, reducing the need for interrogation of the home location register (HLR).

Authentication center (AUC):

The AUC provides authentication and encryption parameters that verify the user’s identity and ensure the confidentiality of each call. The authentication center (AUC) also protects network operators from fraud.

Equipment identity register (EIR):

The EIR database contains information on the identity of mobile equipment to prevent calls from stolen, unauthorized or defective mobile stations.

Message center (MXE):

The MXE is a node that provides integrated voice, fax, and data messaging.

Mobile service node (MSN):

The MSN is the node that handles the mobile intelligent network (IN) services.

Gateway mobile services switching center (GMSC):

A gateway mobile services switching center (GMSC) is a node used to interconnect two networks.

GSM interworking unit (GIWU):

The GIWU consists of both hardware and software that provides an interface to various networks for data communications. Through the GSM interworking unit (GIWU), users can alternate between speech and data during the same call.

Operation and support system (OSS):

The OSS is the functional entity from which the network operator monitors and controls the system. The purpose of operation and support system is to offer support for centralized, regional, and local operational and maintenance activities that are required for a GSM network.

Related articles

• GSM Basic
• What is FTP?
• What is a router?

GSM Basic

Image via Wikipedia

Definition: GSM, which stands for Global System for Mobile communications, reigns as the world’s most widely used cell phone technology. Cell phones use a cell phone service carrier’s GSM network by searching for cell phone towers in the nearby area.

Services Provided by GSM:

From the beginning, the planners of GSM wanted ISDN compatibility in services offered and control signalling used. The radio link imposed some limitations, however, since the standard ISDN bit rate of 64 kbps could not be practically achieved.

Using the ITU­T definitions, telecommunication services can be divided into bearer services, teleservices, and supplementary services. The digital nature of GSM allows data, both synchronous and asynchronous, to be transported as a bearer service to or from an ISDN terminal. Data can use either the transparent service, which has a fixed delay but no guarantee of data integrity, or a non­transparent service, which guarantees data integrity through an Automatic Repeat Request (ARQ) mechanism, but with a variable delay. The data rates supported by GSM are 300 bps, 600 bps, 1200 bps, 2400 bps, and 9600 bps .

The most basic teleservice supported by GSM is telephony. There is an emergency service, where the nearest emergency­service provider is notified by dialling three digits (similar to 911).

Group 3 fax, an analog method described in ITU­T recommendation T.30, is also supported by use of an appropriate fax adaptor. A unique feature of GSM compared to older analog systems is the Short Message Service (SMS). SMS is a bidirectional service for sending short alphanumeric (up to 160 bytes) messages in a store­and­forward fashion. For point­to­point SMS, a message can be sent to another subscriber to the service, and an acknowledgement of receipt is provided to the sender. SMS can also be used in a cell­broadcast mode, for sending messages such as traffic updates or news updates. Messages can be stored in the SIM card for later retrieval .

Supplementary services are provided on top of teleservices or bearer services, and include features such as caller identification, call forwarding, call waiting, multi­party conversations, and barring of outgoing (international) calls, among others.

 

Check More:

1. GSM Architecture
2. GSM Radio Link Aspects
3. GSM Network Aspects
4. GSM vs CDMA