Installing utorrent in ubuntu 16.04

                                           Before viewing the video first of all run these four commands

sudo apt-get update
sudo apt-get  upgrade
sudo apt-get dist-upgrade
sudo apt-get install libssl1.0.0 libssl-dev

Now view the following video and follow the instructions to install utorrent in ubuntu.

xsel | copying pwd command output to clipboard

                                             i found this useful tool xsel which can be used to copy the output of pwd command and much more.

To install this utility just type in following command in the terminal.

This command will install xsel and now you can copy the pwd output to clip board using xsel. See the following video.

That's it.

'performance_schema.session_variables' doesn't exist'

                                                   So i just updated my MySQL from version 5.5 to 5.7 in vagrant box and i wasn't able to connect to MySQL from outside of vagrant. I was using DataGrip and i found this error 'performance_schema.session_variables' doesn't exist'

I googled it and found solution on this stackoverflow page ... awesome it fixed my problem.

just run this command

and then run this command sudo service mysql restart and that's it. 

C++ lower_bound(), upper_bound(), binary_search()

                     

                                                                                   First i'll start with standard template library function binary_search(), this function basically return true or false. it takes the array & element to search as parameter and returns true or false if it's present or not in the array. See the following code.

binary_search()

#include <iostream>
#include <algorithm>

using namespace std;

int main(){
    int A[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int x;
    cout << "Enter the element: " << endl;
    cin >> x;
    if (binary_search(A, A+10, x)){
        cout << "Element is present" << endl;
    } else {
        cout << "Element is not present" << endl;
    }
    return 0;
}

output of the above program on providing following inputs

Enter the element:
4
Element is present

Now as we provided 4 to search and as it's already present in the array .. the answer was as expected! Element is present. Now what if we provide 11 as input which is not present in the array. Let's see the output!

Enter the element:
11
Element is not present

And as expected 11 is not present in the array so the output of the program is Element is not present!

                                                                               binary_search() function is good if we wanna confirm if element is present in the array or not ... but what if we wanna know the index at which the element is present or if it's not persent then the index of the next element. This functionality can be accomplished using STL's lower_bound() & upper_bound().  So let's take lower_bound() next!

lower_bound()

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main(){
    vector<int> A = {1, 2, 3, 4, 6, 7, 8, 9, 10};
    vector<int>::iterator lower;
    int x;
    cout << "Enter the value of x: " << endl;
    cin >> x;
    lower = lower_bound(A.begin(), A.end(), x);
    cout << lower - A.begin() << "\n";
    return 0;
}

Now as you can see we have a sorted vector here, let's get the index of the element which is already present in the vector.

Enter the value of x:
2
1

The index of element 2 is 1 and that is correct! Now let's search for 5 which is not present in the vector.

Enter the value of x:
5
4

And it returned 4 as index for element 5. but as you see vector element 5 is not present! The beauty of this function is that it doesn't show any error it's returns the index of the element which is just bigger then it. Now let's take some cases.

1st case.)  we provide a value which is not present in the vector and is greater then all the elements

Enter the value of x:
121
9

So it adds +1 in the last index and returns it.

2nd case.) we provide a value which is not present in the vector and is smaller then all the elements

Enter the value of x:
-121
0

So it returns the starting index i.e. 0


3rd case.) we provide a vector which has many duplicate values like [1, 2, 3, 4, 5, 5, 5, 6, 7, 8, 9]

Enter the value of x:
5
4

So it returns the first occurence of the element. The element 5 is present at indexes 4, 5, 6. and the lower_bound() functions returns it's lower index or first occurence!

upper_bound()

Now let me add some code for upper_bound() function

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main(){
    vector<int> A = {1, 2, 3, 4, 6, 7, 8, 9, 10};
    vector<int>::iterator upper;
    int x;
    cout << "Enter the value of x: " << endl;
    cin >> x;
    upper = upper_bound(A.begin(), A.end(), x);
    cout << upper - A.begin() << "\n";
    return 0;
}

Now as we have a sorted vector here let's search for an element which is already present in the vector!

Enter the value of x:
2
2

The index returned here by the upper_bound() function is +1 of the original index!

Now let's search for 5 which is not present in the vector!

Enter the value of x:
5
4

And the result here is same as lower_bound. if upper_bound() doesn't find the value then it just returns the index of next greater index!

now let's take some cases here

1st case.) We provide an element which is not present in the vector and is greater then all the elements in the vector!

Enter the value of x:
121
9

Same result as lower_bound(), when it doesn't find the element and all elements are smaller then the element to be found then it returns index + 1 of the last index of the vector

2nd case.) We provide an element which is not present in the vector and is smaller then all elements in the vector!

Enter the value of x:
-121
-121
0

Now this is also same as lower_bound(), when the element we wanna found in smaller the then smallest element of the vector then it returns the index 0.

3rd case.) We provide a vector which has many duplicate values like this [1, 2, 3, 4, 5, 5, 5, 6, 7, 8, 9]

Enter the value of x:
5
7

And this isn't similar to lower_bound(). lower_bound() was returning 4, which is the index of first occurence of element 5. But upper_bound() returns index of last occurence of element + 1


                                                                          That's it! Thanks for your patience!

php sqlite3 driver for PDO!

                                             This one is quite easy. Just run the following command in terminal

New way to do php development

                              Guys, on windows we all use WAMP(Windows, Apache, Mysql, PHP) software stack, while linux users use LAMP stack. But if you're familiar with python or ruby on rails development. They provide inbuilt server for development.. Like python provides SimpleHTTPServer and ROR provide Webrick .... but we use the old school way of development in php. There is a inbuilt server in php which we can use to increase our productivity.

Just move to the directory via terminal and run the following command

That's it, enjoy!

Python SimpleHTTPServer does not serve SVG! [Solved]

                                                                          I was testing one of my web projects in mobile devices and i encountered this problem that it's not serving svg i generated using adobe illustrator! There is problem in mime types in current SimpleHTTPServer. So i'm posting code for a modified version of python SimpleHTTPServer that serve's SVG images :D

That's it. Enjoy!

EDIT => 26 October 2016

hey guys i was learning nginx webserver and i learned about mime-types there so i thought to add some more information here. MIME basically is shortform of Multi-Purpose Internet Mail Extensions. This is basically a file in nginx which has a list of two column values which contains extensions(pdf, svg, jpeg, png, mp3, mp4) and content-type(application/pdf, image/svg+xml etc ..) so if in the servers mime-types file there is no mentioned extention with content-type then its defaults to content-type: application/octet-stream. So in the above case python SimpleHTTPServer does not has extension svg and corresponding content-type: application/svg+xml in its mime-types file that's why its defaults to content-type: application/octet-stream and instead of rendering in browser it downloads.