Ubuntu: How to sort file contents using command ?

In this article, I will share my understanding of sort command with some examples. One important point to notice is that the file contents must be on separate line. If file contains only single line then we are not able to observe the effect of sort command. Before jumping directly to examples, here are some of its variations

To sort file contents                             : sort filename.txt

To sort according to column contents   : sort –k (column number) filename

To sort in reverse order                       : sort –r filename

To remove duplicates while sorting      : sort –u filename

•  Sorting numeric contents

           Suppose file contains only numeric data then file contents are sorted in ascending order of integer values as shown below.

$ cat file

015

004

016

009

003

018

002

020

$ sort file

002

003

004

009

016

018

020

•   Sorting alphabetic contents

            Suppose file contains only alphabetic data then file contents are sorted alphabetically as shown below.

$ cat file

Ashish Gaigole

Siyaram Vishwakarma

Deepak Jaiswal

Dashrath Sharma

$ sort file

Ashish Gaigole

Dashrath Sharma

Deepak Jaiswal

Siyaram Vishwakarma

•  Sorting alpha-numeric contents

           In case file has both numeric and alphabetic data then first all numeric data is sorted in ascending order followed by alphabetic data.

$ cat file

Ashish Gaigole

Siyaram Vishwakarma

Deepak Jaiswal

Dashrath Sharma

015

016

004

009

$ sort file

004

009

015

016

Ashish Gaigole

Dashrath Sharma

Deepak Jaiswal

Siyaram Vishwakarma

•  Sorting file contents according to particular column values

$ cat file

Ashish Gaigole 016 F-42

Siyaram Vishwakarma 015 F-43

Deepak Jaiswal 009 F-44

Dashrath Sharma 004 F-41

$ sort –k 3 file  : file is sorted according to third column in file.

Dashrath Sharma 004 F-44

Deepak Jaiswal 009 F-41

Siyaram Vishwakarma 015 F-43

Ashish Gaigole 016 F-42

$ sort –k 4 file  : file is sorted according to fourth column in file.

Deepak Jaiswal 009 F-41

Ashish Gaigole 016 F-42

Siyaram Vishwakarma 015 F-43

Dashrath Sharma 004 F-44                         

Ubuntu: ”How to recover root password ?”

Situation may arise that you want to login as root user and you don’t  know or you forgot the root password. In this case we need to boot in recovery mode. In some cases recovery mode option will not prompt automatically so need to press left shift key while booting. This will prompt option to boot in recovery mode. Once you boot in recovery mode, various options will be available. 

Selecting root option will login you as root in terminal without any password. Now you can create new root user, you can change the password of existing root user. 

After you have successfully changed the password, you need to reboot the system and now you can login with your new password.

For this just refer following commands.

You can get the list of current user                                 cat  /etc/passwd              

                                                  

You can add new user to the system                              useradd username  

 You can set the password of the user                             passwd username

A HAPPY LIFE or DESERTED ONE….!!

Green house gases absorb the infrared radiations, traps the heat for longer time and makes the atmosphere warmer. It is definitely true that one of the reasons that we are living on earth is because of these green house gases but if we are not careful about their atmospheric levels then they will kill us. According to the latest survey, the amount of greenhouse gases in the atmosphere is highest in last 2 million years. Carbon Dioxide (CO₂) is most harmful among all other green house gases.Before the industrial revolution, the problem was not that much serious. Now a days industrialization has become the benchmark for country’s development, almost every industry results in increasing the amount of green house gas in the atmosphere. The problem is much more serious as carbon levels are increasing exponentially. Previously it takes 7000 years to increase CO₂ level by some amount but now the carbon dioxide has gone up by the same amount in just 55 years.

                                                     What steps we can take as an individual to minimize the effect? As trees absorb CO₂ while photosynthesis we should plant more trees. We can use alternative eco-friendly fuels. We should save electricity, save water, walk whenever possible. If such things are added up by billions of people then definitely it will improve our climatic condition. Everything is in our hand and it’s up to us that what we want? We need to think about our next generation, what type of life you want to give to your generation?  
A HAPPY LIFE or DESERTED ONE….!!

Ubuntu: How to solve “Could not get lock on /var/lib/dpkg/lock“ problem ?

This one of the most frequent problems that arises while updating the installation packages. In order to solve this problem we need to remove the lock file from dpkg directory.as well as cache directory. After removing the lock we can update the packages without any error.

Remove Lock from dpkg    :     sudo rm /var/lib/dpkg/lock

Remove Lock from cache   :     sudo rm /var/cache/apt/archives/lock

Update packages                :     sudo apt-get update

Upgrade packages              :     sudo apt-get upgrade

Ubuntu:Waiting for jockey-backend to exit

After installation of Ubuntu the most common problem is updating or downloading softwares. When we try to update any package or tried to install any software, Ubuntu gives message Waiting for jockey-backend to exit in Update manager. Jockey is tool for installation of third party hardware drivers and need to be disabled safely.

In order to resolve this problem we need to kill this jockey-backend process. Here is solution to do that.

1.Get Administrative access             sudo -i
 
2.Get process id of jockey-backend process    ps -e | grep jockey

3.Kill this process                            kill -9  process_id

Lets Save Precious Water

Water is one of the most precious natural resource that the human beings got. The important thing is how serious we are about its usage?

The amount of water available on the earth is sufficient for human beings if we use it carefully. As population of the earth is increasing exponentially so is the demand of drinking water but we are wasting large amount of water just because currently we are having its sufficient supply. Currently we have to pay for 20 to 30 rupee for one water bottle. The most of the rural areas are still does not have sufficient water supply. They are supplied by water tankers that so not daily. The condition will become much more worsen in the future if we don’t save water. So let’s join our hands to save water as much as possible.

SAVE WATER, SAVE LIFE....!

Implimenting File Sever In Linux

                                          File server can be considered as administrative  storage of shared  resources in the network so that other terminals in the network can access to those resources.

              Here I am implimenting a multithreaded concurrent server.Multithreaded means seperate thread for each client request. One main thread (listen) will continiously run till there are client requests for the files.We have to create seperate thread to service each client request.Concurrent means that server can handle many client requests simultaneously.We also have to impliment mutual exclusion for shared resources.It means that simultaneous reading is possible but  reading while writing or writing while reading is not possible.

                  First we must run server code and then client code. After sucessfully conneted with client , server will display list of available files , will ask whether client want to read or write file  ? In both cases  server will send requested file to client and apply read/write lock on that file so that consistency must  be maintained.In my code ,server is opening file in read mode , reading it and then send it to client.At client end if client want to read the file , display  that file on terminal. If client is writing into file then that change must be reflected into file at server side.For next read request that updated file must be use.

            The main idea is to create socket connection first then we have to handle file read or write request .The functions that i have used for socket creation are  socket(),bind(),connect(),accept() etc and write() and read() for file manipulation.