DEV Community: Sujith V S

Get All Docker Commands

Sujith V S — Tue, 25 Feb 2025 05:12:49 +0000

All Docker Commands

Sujith V S ・ Feb 25

#docker #kubernetes

All Docker Commands

Sujith V S — Tue, 25 Feb 2025 05:12:30 +0000

docker --version: Check the Docker version.

docker help: Display help information for Docker.

Working with Images:

docker pull: Pull an image from a registry.
docker pull <image-name>

docker images: List all images on the local system.

docker build: Build an image from a Dockerfile.
docker build -t <image-name> .

docker rmi: Remove one or more images.
docker rmi <image-name>

docker tag: Tag an image with a new name.
docker tag <source-image> <target-image>

Working with Containers:

docker run: Run a command in a new container.
docker run -it <image-name>

docker ps: List all running containers.
docker ps

docker ps -a: List all containers, including stopped ones.
docker ps -a

docker start: Start one or more stopped containers.
docker start <container-id>

docker stop: Stop one or more running containers.
docker stop <container-id>

docker restart: Restart a container.
docker restart <container-id>

docker rm: Remove one or more containers.
docker rm <container-id>

docker logs: Fetch the logs of a container.
docker logs <container-id>

docker exec: Run a command in a running container.
docker exec -it <container-id> <command>

Networking:

docker network ls: List all networks.
docker network ls

docker network create: Create a new network.
docker network create <network-name>

docker network inspect: Display detailed information on one or more networks.
docker network inspect <network-name>

docker network rm: Remove one or more networks.
docker network rm <network-name>

Volumes:

docker volume ls: List all volumes.
docker volume ls

docker volume create: Create a new volume.
docker volume create <volume-name>

docker volume inspect: Display detailed information on one or more volumes.
docker volume inspect <volume-name>

docker volume rm: Remove one or more volumes.
docker volume rm <volume-name>

Docker Compose:

docker-compose up: Build, create, start, and attach to containers.
docker-compose up

docker-compose down: Stop and remove containers, networks, images, and volumes.
docker-compose down

docker-compose build: Build or rebuild services.
docker-compose build

docker-compose ps: List containers.
docker-compose ps

docker-compose exec: Execute a command in a running container.
docker-compose exec <service-name> <command>

Docker System Management:

docker system df: Show docker disk usage.
docker system df

docker system prune: Remove unused data.
docker system prune

Pagination CDN setup guide for ejs template engine.

Sujith V S — Sun, 08 Sep 2024 18:42:20 +0000

To implement pagination in the ejs template engine, follow these steps.

Step 1: Include the Pagination CDN
Add the following script at the bottom of your EJS file:

<script src="https://cdn.jsdelivr.net/gh/SujithVSuresh/pagination-cdn@master/pagination.js"></script>

Step 2: Add Pagination Controls to Your Template
Add the following code where you want the pagination buttons to appear:

          <div class="d-flex justify-content-center">
            <nav aria-label="Page navigation example">
              <ul class="pagination">
                <li class="page-item" id="prevBtn"><a class="page-link text-black" href="#">Previous</a></li>
                <% for(let i=1; i<= totalPages; i++){ %>
                <li class="page-item pagenationBtn" data-page-no="<%= i %>"><a class="page-link text-black"><%= i %></a></li>
                <% } %>
                <li class="page-item" total-pages="<%= totalPages %>" id="nxtBtn"><a class="page-link text-black" href="#">Next</a></li>
              </ul>
            </nav>
          </div>

The above code provides the interface for pagination. Ensure that you align and style the content properly according to your application's design.

Step 3: Install and setup paginationx npm package for nodejs. Follow this guide

NPM Package & CDN for Pagination in Javascript / Nodejs

Sujith V S — Sun, 08 Sep 2024 18:33:46 +0000

Hello, I am someone who dislikes repetitive tasks, so to streamline the process of implementing pagination, I developed an npm package named paginationx for the backend use and a CDN for frontend integration. These tools simplify pagination setup and save time by eliminating the need to write the same code repeatedly.

In this article will be doing only 2 steps,

To setup the npm package for the nodejs backend.
To setup the cdn for pagination in the ejs template frontend.

1. NPM Package Implementation
To use the paginationx npm package for Node.js, follow these steps:

Step 1: Install Paginationx npm package

npm i paginationx

Step 2: Import the module and use them in your controller.

const pagination = require("paginationx")

const users = async (req, res) => {
  try {
    const paginate = await pagination(User, 2, req.query)

    res.render("admin/user", {
      users: paginate.data,
      totalPages: paginate.totalPages,

    });
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
};

In the code above, we are passing three arguments to the pagination function:

First argument: The model name representing the data that we need to apply pagination to.
Second argument: Number of items to be shown on a single page.
Third argument (optional): Pass the req.query data. Use req.query only if you are using the pagination CDN to handle pagination on the frontend.

The pagination function (const paginate = await pagination(User, 2, req.query)) returns paginated data and total pages:

To access the paginated data, use pagination.data.
To access the total number of pages, use pagination.totalPages.

Step 3: Pass the paginated data and total pages count to the ejs.

{
      users: paginate.data,
      totalPages: paginate.totalPages,
}

Note: Key for passing total pages should exactly be totalPages.

2. Pagination CDN Implementation

To implement pagination in the ejs template engine, follow these steps.

Step 1: Include the Pagination CDN
Add the following script at the bottom of your EJS file:

<script src="https://cdn.jsdelivr.net/gh/SujithVSuresh/pagination-cdn@master/pagination.js"></script>

Step 2: Add Pagination Controls to Your Template
Add the following code where you want the pagination buttons to appear:

          <div class="d-flex justify-content-center">
            <nav aria-label="Page navigation example">
              <ul class="pagination">
                <li class="page-item" id="prevBtn"><a class="page-link text-black" href="#">Previous</a></li>
                <% for(let i=1; i<= totalPages; i++){ %>
                <li class="page-item pagenationBtn" data-page-no="<%= i %>"><a class="page-link text-black"><%= i %></a></li>
                <% } %>
                <li class="page-item" total-pages="<%= totalPages %>" id="nxtBtn"><a class="page-link text-black" href="#">Next</a></li>
              </ul>
            </nav>
          </div>

The above code provides the interface for pagination. Ensure that you align and style the content properly according to your application's design.

How to customise the pagination button?
You can give custom styles to the pagination button, but you have to strictly include some of the class, id and properties, inorder to make that pagination works properly in the frontend.
Here we have three kinds of button:

Previous button
Collection of page number button
Next button

Next lets look what all id, class and properties should be included in each of these button to make it work well.

Previous button:

<li id="prevBtn"><a>Previous</a></li>

The above code can be considered as the base cod for the previous button section. Inside the li tag an id with name 'prevBtn' should be provided.

Page number button:

<% for(let i=1; i<= totalPages; i++){ %>
     <li class="pagenationBtn" data-page-no="<%= i %>">
     <a><%= i %></a>
     </li>
<% } %>

The above code can be considered as the base code for the page number button section. li tag should be inside the for loop to show all the page number available. In the li tag you should include the class named 'pagenationBtn' and the data-page-no="<%= i %>" attribute.

Next button: The below code can be considered as the base code for the next button. In the li tag you should include the id named 'nxtBtn' and the total-pages="<%= totalPages %>" attribute.

<li total-pages="<%= totalPages %>" id="nxtBtn"><a>Next</a></li>

Pointer and Array in C programming.

Sujith V S — Thu, 04 Jan 2024 23:49:00 +0000

Printing corresponding address of each element of an array.

int main() {

    int numbers[5] = {1, 2, 5, 8, 3};

    for (int i=0; i<5; i++){
        printf("%d = %p\n", numbers[i], &numbers[i]);
    }
    return 0;
}

Output:

1 = 0x7ffffa8cf140
2 = 0x7ffffa8cf144
5 = 0x7ffffa8cf148
8 = 0x7ffffa8cf14c
3 = 0x7ffffa8cf150

Printing array elements address without index value.

int main() {

    int numbers[5] = {1, 2, 5, 8, 3};

    printf("Array address: %p", numbers);
    return 0;
}

Output:

Array address: 0x7ffcf4fe97c0

The memory address of the first array element and the address of the array is the same.This is because the address of the array always points to the first element of the array.
Also in the above code to print the array address we have used only the name of the array instead of the & sign. This is because in most context array names are by default converted to pointers and we can directly use name of the array without & sign.

Print other array elements address without index value
printf("Array address: %p", numbers + 1); - this will print the second element.
printf("Array address: %p", numbers + 2); - this will print the third element.

Printing array element's memory address using for loop without index value.

int main() {

    int numbers[5] = {1, 2, 5, 8, 3};

    for (int i=0; i<5; i++){
        printf("%d = %p\n", numbers[i], numbers + i);
    }

    return 0;
}

Output:
1 = 0x7ffccb8a1d70
2 = 0x7ffccb8a1d74
5 = 0x7ffccb8a1d78
8 = 0x7ffccb8a1d7c
3 = 0x7ffccb8a1d80

Access array element using pointer.
In order to use array elements using pointers, we have to use *(numbers + i)

int main() {

    int numbers[5] = {1, 2, 5, 8, 3};

    for (int i=0; i<5; i++){
        printf("%d = %p\n", *(numbers + i), numbers + i);
    }

    return 0;
}

Output:

1 = 0x7fff49ac30b0
2 = 0x7fff49ac30b4
5 = 0x7fff49ac30b8
8 = 0x7fff49ac30bc
3 = 0x7fff49ac30c0

*Change array elements using pointers *

int main() {

    int numbers[5] = {1, 2, 5, 8, 3};

    *numbers = 76;
    *(numbers + 1) = 89;

    printf("%d ", *numbers);
    printf("%d", *(numbers+1));

    return 0;
}

Pointers in C programming.

Sujith V S — Thu, 04 Jan 2024 11:56:33 +0000

Pointer in c allow us to work directly with the computer memory.

Memory Addresses

In c programming whenever we declare a variable a space will be allocated in the memory for the variable and C allows us to access the address of the variable. We use & with variable name to access the memory address.
Example:

int main() {
    int age = 25;
    printf("%p", &age);
    return 0;
}

Output:

0x7ffcad58272c

The format specifier %p(pointers) and & is used to get the memory address where 25 is located.

scanf("%d", &age);- with scanf we are instructing the compiler to store the input value at the memory address specified by this &age.

Pointer Variable

The pointer variable stores the memory addresses of the available value.
Example: int* ptr;

Assigning value(memory address) to a pointer variable

int main() {
    int age = 25;
    printf("%p", &age);

    int* ptr = &age; //assigned value.

    printf("\n%p", ptr);
    return 0;
}

Access value using pointer
Here we are trying to access the value of a variable using pointer variable.

int main() {
    int age = 25;

    int* ptr = &age; 

    printf("Address: %p\n", ptr);

    printf("Value: %d", *ptr); 

    return 0;
}

printf("Value: %d", *ptr);- it gives the value stored in a memory address.

Change value using pointer

int main() {
    int age = 25;

    int* ptr = &age; 

    *ptr = 31; 

    printf("%d", age);

    return 0;
}

In the above code, the initially assigned value is 25.
*ptr = 31; - it assigns a new value pointed by the ptr variable.
printf("%d", age); - now the value is changes to 31. because it points directly to the address and change the value to 31.

int* ptr = 32; (Invalid)
ptr is a pointer and it can only store memory address. And if we try to assign a value or number to it then it will become invalid.

*ptr = &number; (invalid)
*ptr stores the value and if we try to assign a memory address then it becomes invalid.

ptr = &number; (valid) - assigning address.

*ptr = number; (valid) - assigning value.

String functions in C programming.

Sujith V S — Wed, 03 Jan 2024 14:01:49 +0000

To use the string functions, we have to use <string.h> header file.

strlen()

#include <string.h>

int main() {
    char str[] = "Hello, World!";
    int length = strlen(str);
    printf("Length of the string: %d\n", length);
    return 0;
}

strcpy()

This function is used to copy one string to another.

#include <string.h>

int main() {
    char food[] = "Pizza";
    char bestFood[strlen(food)];
    strcpy(bestFood, food);
    printf("%s", bestFood);
    return 0;
}

strcpy(bestFood, food);
Here first argument is the variable we want to put the copied string. Second argument is the variable in which we want to copy the string.

strcat()

This is used to join two string together.

#include <string.h>

int main() {
    char str1[] = "Hello, ";
    char str2[] = "world!";

    strcat(str1, str2);

    printf("%s", str1);

    return 0;
}

To concatenate second string to the first string.

strcmp()

String comparison function to check if two strings are equal. If this function returns 0 then it can be considered as equal.

#include <string.h>

int main() {
    char text1[] = "abcd";
    char text2[] = "abcd";

    int result = strcmp(text1, text2);

    printf("%d", result);

    return 0;
}

These are just a few examples, and there are more string manipulation functions available in the C standard library <string.h>

String in C programming.

Sujith V S — Wed, 03 Jan 2024 13:44:41 +0000

String is a collection of characters that are used to represent textual data.

int main() {
    char str[] = "Sujith";
    printf("%s", str);
    return 0;
}

Use %s format specifier for printing string.
Every string in c ends with \0. This null character helps the compiler to know the end of the string. So actual size of the string will be 1 greater than the total no;of character in the string.

String Input

int main() {

    char str[20];

    printf("Enter your name here: ");

    scanf("%s", str);

    printf("%s", str);

    return 0;
}

In order to take the input, we don't need to use & for string because str is an array and it already points to the first element of str.

The scanf method can only take input until it encounters white spaces. So not possible to take input like "Steve Jobs". So to take all the inputs we can use:
fgets(str, sizeof(str), stdin)
str - string name
sizeof(str) - size of string.
stdin - it means standard input. It denotes we are taking input from the keyboard.

Access characters of string

int main() {

    char str[] = "Sujith";

    printf("%c", str[0]); 

    return 0;
}

Since we are only printing single character use %c format specifier

Changing elements of a string.

int main() {

    char str[] = "Sujith";

    str[2] = 'J';
    str[4] = 'T';

    printf("%s", str);
    return 0;
}

Multi-dimensional Array

Sujith V S — Wed, 03 Jan 2024 05:59:17 +0000

Each element of multi dimensional array is an array. This is why it is called as array of arrays.

Syntax:
int arr[2][3];

int - datatype
arr - name of array.
2 - there will be two arrays inside this array.
3 - each array will have 3 elements.

int arr[2][3] = {{1,2,3}, {6,7,8}};

Access array elements

int arr[2][3] = {{1,2,3}, {6,7,8}};

    printf("%d ", arr[0][0]); 
    printf("%d ", arr[1][2]);

Here 1 is the second array and 2 is the third element in this array.

Change array values.

int main() {

    int arr[2][3] = {{1,2,3}, {6,7,8}};

    arr[0][2] = 7;
    arr[1][1] = 8;

    printf("%d", arr[0][2]);
    printf("%d", arr[1][1]);

    return 0;
}

Multidimensional array using for loop

#include <stdio.h>

int main() {

    int arr[2][3] = {{1,2,3}, {6,7,8}};

    for(int i=0; i<2; i++){
        for(int j=0; j<3; j++){
            printf("%d ", arr[i][j]);
        }
    }

    return 0;
}

First for loop for each arrays inside and the second for loop is for the elements inside each array.

Array in C programming.

Sujith V S — Wed, 27 Dec 2023 11:38:31 +0000

An array is a collection of single type of data.

Syntax:
datatype arrayName[arraySize];

Assigning values to array.

int age[5] = {56, 45, 87, 23, 54};

We can also remove the size of the array so that the compiler will automatically determine the size of the array by counting the elements inside thew curly bracket.
int age[] = {56, 45, 87};

If the size of an array is 5 and we adds only 3 value to it then the remaining two values will be occupied by 0.
int age[5] = {56, 45, 87};

Access array elements.

In c programming each element of an array is represented with a value known as index value. Index value starts with 0, therefore the first element of an array will have the index value 0.

To access the element in an array we use:
arrayName[index]
Example:

int age[5] = {56, 45, 87, 89, 54};

printf("%d", age[0]);

Assign values using index number.

int age[5];

age[0] = 22;
age[1] = 65;
age[2] = 43;
age[3] = 56;
age[4] = 26;
age[5] = 89;

Assign values to an array from user input

int age[5];

printf("Enter 5 input values: ");
scanf("%d", &age[0]);
scanf("%d", &age[1]);
scanf("%d", &age[2]);
scanf("%d", &age[3]);
scanf("%d", &age[4]);
scanf("%d", &age[5]);

Changing array elements.

#include <stdio.h>

int main() {

    int age[5] = {4, 56, 8, 43, 6};

    //changing array elements.
    age[2] = 26;

    printf("%d", age[2]);

    return 0;
}

In the above code, we have changed the value 8 to 26. The index value of 8 is 2.

Loops in array

We can use loops in C programming to assign or print values in an array.

#include <stdio.h>

int main() {

    int age[5];

    for(int i=0; i<5; i++){
        scanf("%d", &age[i]);
    }

    for(int i=0; i<5; i++){
        printf("%d", age[i]);
    }

    return 0;
}

Index out of Bound Error

If we try to access array outside of its bound or limit or allocated memory space then it can cause error.
Example:

int age[5];

for(int i=0; i<5; i++){
        scanf("%d", &age[i]);
    }

for(int i=0; i<6; i++){
   printf("%d ", age[i]);
}

Output:

8 6 5 4 3 32764

In the above code the size of an array is 5. And in the second loop we are trying to access the 6th element of the array named age. Therefore this caused the index out of bound error and prints the value 32764.

Recursion in C programming.

Sujith V S — Wed, 27 Dec 2023 11:08:26 +0000

A function that calls itself is called recursion function.

Syntax:

void recurse(){
    ....
    recurse();
    ...    
}

int main(){
    ....
    recurse();
    ....
    return 0;
}

In the above code the function recurse() will call itself again and again.
To prevent it we can add if else statement.

void recurse(){
    if(condition){
    ....
    }
    else{
    recurse();
    }
    ...    
}

Task 1: Program to find the sum of n natural numbers.

#include <stdio.h>

int main() {

    int number, result;

    printf("Enter a number: ");

    scanf("%d", &number);

    result = findSum(number);

    printf("Sum = %d", result);

    return 0;
}

int findSum(int num){
    if(num!=0){
        return num + findSum(num - 1);
    }else{
        return 0;
    }
}

Task 2: Program to find the factorial of a number:

#include <stdio.h>

int main() {

    int number, result;

    printf("Enter a number: ");

    scanf("%d", &number);

    result = findSum(number);

    printf("Sum = %d", result);

    return 0;
}

int findSum(int num){
    if(num!=0){
        return num * findSum(num - 1);
    }else{
        return 1;
    }
}

Standard library functions in C programming.

Sujith V S — Thu, 21 Dec 2023 18:11:26 +0000

Standard library functions are predefined function which is already defined inside a file and we can directly use them in our program.

Input / Output functions

printf()
printf() is a standard library function which is defined in the stdio.h header file. So that is why <stdio.h> is included in our program file.

#include <stdio.h>

int main() {

    printf("Hello world");

    return 0;
}

Other I/O functions in C are:
scanf(): Reads formatted input from the console.
getchar(): Reads a single character from the console.
putchar(): Writes a single character to the console.
fopen(): Opens a file.
fclose(): Closes a file.
fread(): Reads data from a file.
fwrite(): Writes data to a file.

Mathematical functions

sqrt()
sqrt() is a standard library function which is defined in the <math.h> header file. It is used to calculate the square root of a number.

#include <stdio.h>
#include <math.h>

int main() {

    int num = 25;
    printf("Square root %lf", sqrt(num));

    return 0;
}

cbrt()
cbrt() is a standard library function which is defined in the <math.h> header file. It is used to calculate the cube root of a number.

#include <stdio.h>
#include <math.h>
int main() {

    int num = 27;
    printf("Cube root %lf", cbrt(num));

    return 0;
}

pow(a, b)
In C, pow(a, b) is used to calculate the a raised to the power of b. It's available in the <math.h> header file and takes two arguments.
a: The base value
b: The exponent

#include <stdio.h>
#include <math.h>
int main() {

    int a = 5;
    int b = 2;

    double result = pow(a, b);
    printf("Power: %lf", result);

    return 0;
}

Other mathematical functions in C are:
abs(): Returns the absolute value of a number.
sin(): Calculates the sine of an angle.
cos(): Calculates the cosine of an angle.

Character handling functions

toupper()
toupper() is a standard library function which is defined in the <ctype.h> header file. It is used to convert a lowercase letter to its uppercase equivalent.

#include <stdio.h>
#include <ctype.h>

int main() {
    char alpha = 'e';
    char upper = toupper(alpha);
    printf("%c", upper);
    return 0;
}

Other character handling functions in C are:
isalpha(): Checks if a character is an alphabet.
isdigit(): Checks if a character is a digit.
isupper(): Checks if a character is uppercase.
islower(): Checks if a character is lowercase.
tolower(): Converts a character to lowercase.

Apart from the standard library functions that are mentioned above, there are many other standard library functions in C programming which are used for important operations. The remaining functions will be discussed in the upcoming posts.