VI Editor Commands and Networking Commands in Linux

VI Editor Commands and Networking Commands in Linux
2. Vi Editor & its Modes, Introduction of Basic administrative commands.

  • i – Insert at cursor (insert mode)
  • ESC – Terminate insert mode
  • a – Write after cursor (append mode)
  • A – Write at the end of line
  • U – Undo all changes to the entire line
  • u – Undo last change
  • o -new line
  • dd – Delete line
  • 3dd – Delete 3 lines.
  • dw – Delete word
  • cw – Change word
  • 4dw – Delete 4 words
  • x – Delete character at the cursor
  • r – Replace character

Moving Cursor in a file

  • k – Move cursor up
  • j – Move cursor down
  • h – Move cursor left
  • l – Move cursor right

Saving and Closing the file

  • Shift+zz – Save the file and quit
  • :w – Save the file but keep it open
  • :q  – Quit without saving
  • :wq – Save the file and quit
  • :q! – Force Quit, no save

Linux File Permissions
Read (r)
Write (w)
Execute (x)
In Linux, each file is associated with an owner and a group and assigned with permission access rights for three different classes of users
u – owner.
g – group.
o – All other users.
a – All users, identical to ugo.

– Removes the specified permissions.
+ Adds specified permissions.
= Changes the current permissions to the specified permissions.

Each read, write, and execute permissions have the following number value:
r             (read) = 4
w           (write) = 2
x        (execute) = 1
no permissions = 0

To find out the file’s permissions in numeric mode simply calculate the totals for all users classes
Owner: rwx=4+2+1=7
Group:   r-x=4+0+1=5
Others:  r-x=4+0+0=4

Give the file’s owner read and write permissions and only read permissions to group members and all other users:
$ chmod 644 File1
Give the file’s owner read, write and execute permissions, read and execute permissions to group members and no permissions to all other users:
$ chmod 750 File2
To change the permissions of all files and subdirectories under the /var/www directory to 755 you would use:
$ chmod -R 755 /var/www

3. Usage of basic Network related commands in Linux.
Ping(Packet Internet Groper)
ping command is used to ensure that a computer can communicate to a specified device over the network.
$ ping
$ ping

nslookup command queries the DNS in order to fetch the IP address or the domain name from DNS records.
$ nslookup

This command is used to get the route of a packet.
$ traceroute

host command is used to find domain name associated with the IP.
$ host
$ host

netstat(Network Statistics) is the command that is used to display routing table, connection information.
$ netstat
$ netstat -r

ARP(Address Resolution Protocol) command is used to display of IP address to MAC address.
$ arp

Show ip address
$ ifconfig

To enable an interface
ifup eth0
To disable an interface
ifdown eth0

Linux iwconfig is used to configure the wireless network interface. It is used to set and view the basic WI-FI details like SSID and

4. How to Check if a File Exists.
To test for the file /tmp/test.log, enter the following from the command line:
test –f /tmp/test.txt
The first line executes the test to see if the file exists. The second command, echo, displays the results 0 meaning that the file exists, 1 means no file was found.
echo $?
In our example, the result was 1.
[email protected]:~$ echo $?

Now try creating a file, then testing for it:
touch /tmp/test.txt
test –f /tmp/test.txt
echo $?
As we have created the file beforehand, the result now is 0:
[email protected]:~$ test –f /temp/test.txt
[email protected]:~$ echo $?

You can also use square brackets instead of the test command:
[ –f /tmp/test.txt ]
echo $?
How to Check if a Directory Exists
To check if a directory exists, switch out the –f option on the test command for –d (for directory):
test –d /tmp/test
echo $?
Create that directory, and rerun the test:
touch /tmp/test
test –d /tmp/test
echo $?

Create and Execute First BASH Program:

Open Source Software Lab Manual 

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