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.

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