fread() Function in C

Syntax of fread() Function in C

The syntax of fread() in C is given below:

size_t fread(void *ptr, size_t size, size_t count, FILE *stream);

Parameters of fread() C

There are different types of parameters in fread() function in C:

• ptr is a void-type pointer that points to the block of memory. This block of memory is a place where our data will be stored.
   
• size indicates the size in bytes of each element that needed to be read. 
   
• count indicates the number of elements to read.
   
• stream is a pointer to the FILE object representing the file to read from.
   

Return Value of fread() function in C

When we execute this function, it will return a number. This number indicates the number of items successfully read. While executing this function, if an error comes, then it will return a number. This number will be less than the number of items requested to read.

Let us understand fread C with some examples.

Examples of C fread() function 

Here are some examples by using the fread C. 

Reading Data from a Text File

In this example, we will understand how fread C function works while reading a text file. There are some steps that we need to do before writing the code.

Step 1: We have to create a file. We have created a file with the name ninjas.txt. 

Step 2: Then we can write something in it manually or by using fwrite() function. So, we have written this:

Hello Ninjas, How are you doing today?
This is a fread C example.

Step 3: Now, we will write our code for reading this file by using fread C.

#include <stdio.h>
int main() {
     // Creating a buffer
    char buffer[100];

    // Opening the file ninjas.txt
    FILE *file = fopen("ninjas.txt", "r");

    // If file is not created
    if (file == NULL) {
        printf("Oops! File not found.");
        return 1;
    }

    // If a file is there, then fread C will work
    while(fread(buffer, sizeof(char), sizeof(buffer), file) != 0) {
        printf("%s", buffer);
    }

     // Closing the file
    fclose(file);
    return 0;
}

You can also try this code with Online C Compiler

Run Code

Output

Explanation

In this example, we have discussed a program in C that uses fread C to read the data from the file ninjas.txt. This file contains a string of characters. That’s why we have created a buffer of 100 characters to store this data. Then we have used a function to open the file, i.e., fopen(). We have opened this file in read mode by providing the ‘r’ in fopen() function. Then we have created a while loop that reads the data from the file by using the fread C.

Reading Data From a Binary File

In this example, we will understand how the fread C function works while reading a binary file. There are some steps that we need to do before writing the code.

Step 1: We have to create a binary file. We have created a file with the name ninjasdetails.bin.

Step 2: Then we have to write something in it manually or by using fwrite() function. So, we have written this:

Narayan 20 400

Step 3: Now, we will write our code for reading this binary file by using fread C.

#include <stdio.h>

// Ninja Details
struct Ninja {
    char name[20];
    int age;
    int questionsSolved;
};

int main() {
    struct Ninja ninja;
    // Opening the ninjasdetails.bin file
    FILE *file = fopen("ninjasdetails.bin", "rb");
   // If file not found
    if (file == NULL) {
        printf("Oops! File not found.");
        return 1;
    }

    // If file found then start reading
    while(fread(&ninja, sizeof(struct Ninja), 1, file) != 0) {
        printf("Name: %s\nAge: %d\nQuestions Solved: %d\n\n", ninja.name, ninja.age, ninja.questionsSolved);
    }

    // Closing the file
    fclose(file);
    return 0;
}

You can also try this code with Online C Compiler

Run Code

Output

Explanation

In this example, we have discussed a program in C that uses fread C to read the data from the binary file ninjasdetails.bin. This file contains details of ninjas, such as name, age, and the number of questions they have solved. That’s why we have created a structure Ninja to store this data. Then we have used a function to open the file, i.e., fopen(). We have opened this file in read-in binary mode by providing the ‘rb’ in fopen() function. Then we created a while loop that reads the data from the binary file by using the fread C.

Also see, Short int in C Programming

Frequently Asked Questions

What is the difference between fread and Fscanf?

fread is used to read raw binary data from a stream, while fscanf reads formatted input, parsing it according to specified format specifiers.

What is the difference between read and fread in C?

read is a system call that performs low-level I/O operations, directly interfacing with the OS. fread is a higher-level function that reads data from a file stream, handling buffering and type conversion.

How is fread C different from fgets()?

fread C and fgets() are both standard library functions in C. fread C is used to read binary data from a file. On the other hand, fgets() is used to read text data from a file. 

What happens if fread C encounters an error while reading a file?

While reading, if an error occurs, this will return a number that will be less than the number of items requested to read, or else it will return 0.

Conclusion

In this article, we have learned about the `fread()` function in C, which is a powerful tool for reading binary data from files. By specifying the size and number of elements to read, `fread()` efficiently populates an array with data from an input stream. The knowledge of `fread()` is very important for every programmer who is working with file I/O and binary data manipulation in C, at last, we saw different examples of using this function. 

• fseek() Function in C
   
• fputs() and fgets in C
   
• fputc() and fgetc in C
   
• Getch in C
   
• Bubble Sort Program in C
   

We hope this blog helped you to understand the concept of fread C. 

To practice and improve yourself in the interview, you can also check out Top 100 SQL problems, Interview experience, Coding interview questions, and the Ultimate guide path for interviews.