Practice session on UNIX commands and vi editor

Aim: To practice UNIX commands and vi editor

Description:

            Linux is an open source operating system like other OS such as Ms windows, Apple, Mac OS, Google, Android.

            Unix is also an OS like Linux. But it is a commercial OS. It consists of three parts,

1.Kernal

2.Shell

3.Programs

Linux Shell or Terminal:

            A shell is a program that receives commands from the user and gives it to the OS to process and it shows the output.

ü  The commands are executed in the Linux terminal.

ü  The terminal is a command Line interface to interact with the system which is similar to the command prompt in the windows OS.

ü  Commands in Linux are case sensitive.

Telnet 192.168.7.2

Login:  cse21-d5

Password: cse21-d5

            [cse21-d5 @localhost ~]$

Pwd command:

            The pwd command is used to display the location of the current working directory.

            Syntax- pwd

            [cse21-d5 @localhost~]$ pwd

                        /home/cse21/cse21-d5

Everything on the linux system is located at root directory.

date command:

            The date command is used to display the date, time, time zone, and more.

            Syntax- date

            [cse21-d5 @localhost~]$ date

            Sun Jan 1 01:25:22 IST 2006

cal command:

            The cal command is used to display the current months calendar with the current date highlighted.

            Syntax- cal

            [cse21-d5 @localhost~]$ cal

time command:

            The time command is used to display the time to execute a command.

            Syntax- time

            [cse21-d5 @localhost~]$ time

            real omo.ooos

            user omo.ooos

            sys omo.ooos

ls command:

            The ls command is used to display the list of content of a directory.

Syntax- ls

            [cse21-d5 @localhost~]$ ls

 

mkdir command :

            The mkdir command is used to create a new directory.

            Syntax- mkdir <directory name>

            [cse21-d5 @localhost~]$ mkdir cse

            [cse21-d5 @localhost~]$ ls

            Output: cse

cd command:

            The cd command is used to change the current directory.

            Syntax- cd <directory name>

            [cse21-d5 @localhost~]$ cd cse

            [cse21-d5 @localhost cse]$

rmdir command:

            The rmdir command is used to delete a directory.

            Syntax- rmdir <directory name>

            [cse21-d5 @localhost~]$ cd cse/cse-b

[cse21-d5 @localhost~]$ cd ..

[cse21-d5 @localhost~]$ rmdir cse-b

[cse21-d5 @localhost~]$ ls

touch command:

            The touch command is used to create empty files.

We can create multiple empty files by executing it only once.

Syntax- touch <file name>

            Touch <file.1><file.2>……….

            [cse21-d5 @localhost~]$ touch  sample

[cse21-d5 @localhost~]$ touch

[cse21-d5 @localhost~]$ 5D0 5C1 5C2

[cse21-d5 @localhost~]$ ls

Ouput : 5D0 5C1 5C2 sample

ls-l command:

            This command gives more information.

[cse21-d5 @localhost~]$ ls-l

Output:

Total 0

-rw-r—1 cse20 0 mar11 12:17 5D0

-rw-r—1 cse20 0 mar11 12:17 5C1

-rw-r—1 cse20 0 mar11 12:17 5C2

-rw-r—1 cse20 0 mar11 12:17 sample

ü  The first column represents file type and the permission given on the file.

ü  The second columns represents the number of memory blocks taken by the file or directory

ü  The third column represents the owner of the file

ü  The fourth column represents the group of owners.

ü  The fifth column represents the file size in bytes.

ü  The sixth column represents the date and time of when the file was created or modified for the last time

 

meta characters:

* :   This character is used to match zero or more characters.

?: This symbol matches zero or one character.

[cse21-d5 @localhost cse]$ ls 5*

5D0:

5C1:

5C2:

[cse21-d5 @localhost cse]$ ls 5D?

5D0

cat command:

The cat command is used to create file, display content of the file, copy the content of one file to another file and more.

            Syntax- cat [option] [file name]

            cat  <filename>

            //enter file content

ü  This command is used to modify or enter some data into file.

ü  Press “CTRL+D” keys to save file.

ü  To display contents of the file the command is cat filename

[cse21-d5 @localhost cse]$ cat> sample

hi

hello

[cse21-d5 @localhost cse]$ cat sample

hi

hello

cp command:

            This command is used to copy a file to another file.

            Syntax- cp sourcefile destination file

            [cse21-d5 @localhost cse]$ cp sample 5D0

[cse21-d5 @localhost cse]$ cat 5D0

hi

hello

rm command:

            this command is used to remove a file.

            Syntax- rm filename

[cse21-d5 @localhost cse]$ rm 5C1?

[cse21-d5 @localhost cse]$ ls

clear command:

            This command is used to clear the terminal screen

            Syntax- clear

exit command:

            This command is used to close or exit from the current shell or terminal.

            Syntax- exit

tac command:

            This command is used to print the content of file in reverse order.

            Syntax- tac <filename>

[cse21-d5 @localhost~]$ cat 5C1

1

2

3

4

[cse21-d5 @localhost ~]$ tac 5C1

4

3

2

1

head command:

            This command displays the first ten lines of the file.

            Syntax- head <filename>

[cse21-d5 @localhost ~]$ head 5C1

tail command:

            This command displays the last ten lines of the file.

            Syntax- tail <filename>

[cse21-d5 @localhost ~]$ tail 5C1

host command:

            It is used to display the ip address for a given domain name and vice versa.

            Syntax- host <domain name> or <ip address>

 [cse21-d5 @localhost ~]$ host

sort command:

            The sort command is used to sort the data in alphabetical order.

            Syntax- sort <filename>

wc command:

            This command is used to count the number of lines, words, characters.

            Syntax- wc <filename>

[cse21-d5 @localhost ~]$ wc-la

3 a

[cse21-d5 @localhost ~]$ wc-wa

4 a

[cse21-d5 @localhost ~]$ wc-ca

7 a

[cse21-d5 @localhost ~]$ wc a

3 4 7 a

mv command:

            This command is used to move the file from one location to another locxation.

            Syntax- mv filename destination filepath

[cse21-d5 @localhost ~]$ cd cse mkdir gec

[cse21-d5 @localhost ~]$ ls

5C2 5C3 cse gec sample

[cse21-d5 @localhost ~]$ mv sample gec

[cse21-d5 @localhost ~]$ cd gec

[cse21-d5 @localhost gec]$ ls

Sample

[cse21-d5 @localhost ~]$ cd ..

[cse21-d5 @localhost ~]$ ls

5C2 5C3 cse gec

vi editor:

It is used to edit an existing file or create a new file from scratch. It is also used to just read a text file.Syntax- vi <text file>

ü  A tilde (~) can be seen on each line following the cursor. A tilde represents an unused line.

ü  If a tilde does not begin and appears to be blank there is a space, tab , newline or some other non-viewable character present.

shell script:

            A shell provides you with an interface to the Unix system.

ü  A shell is a command line interpreter and typical operations performed by shell scripts include file manipulation, program execution and printing text

ü  A shell is an environment in which we can run our commands , programs and shell scripts.

ü  A shell script is a computer program designed to be run by the unix/ Linux shell.

ü  All the scripts would have the –sh extension.

Operation Modes:

·         Command mode: This mode enables to perform administrative tasks such as saving the files, executing the commands, moving the cursor.

·         Insert mode: This mode enables to insert text into the file. Everything that is typed in this mode is interpreted as input and placed in the file.