C Program to Read a Line from a File and Display it as Output

C program to read a line from a file and display it as output.

In this article, you will learn how to read lines from a given file step-by-step.

To solve this problem we'll take an input file named 'hello.txt' with some sample paragraphs and open this file in the given C program.

INPUT FILE - `hello.txt`, contents in the input file

You should know about the following topics in C programming to understand this program:

• C For loop
• C While loop
• C Pointers
• C File System

Source

// C Program to Read a Line from a File
#include <stdio.h>
#include <stdlib.h>

// It's the main function of the program
int main() {
    // Step-1 Open a file named 'hello.txt' by creating a file pointer
    FILE* file_string = fopen("./hello.txt", "r");

    // Step-2 Buffer to store the each line of the opened file
    char sentence[256];

    // Step-3 Check if file didn't open
    if (file_string == NULL) {
        fprintf(stderr, "Unable to open file!\n");
    }

    // Step-4 If the file is opened then read each line of the opened file
    else {
        printf("Opened file string: 'hello.txt'\n");
        printf("-----------------------------------------------------------------------\n\n");

        // Iterate over each line of the file and store into 'sentence' Buffer
        while (fgets(sentence, sizeof(sentence), file_string)) {
            // Print each line of the file
            printf("%s", sentence);
        }

        // Close the opened file when the file stream is completed
        fclose(file_string);

        printf("\n\n-----------------------------------------------------------------------\n");
    }
    return 0;
}

Run

Output

Explanation

1. Created a file pointer 'file_string' and opened the input file 'hello.txt' using open() function.
2. Declared a buffer variable to store each line of the opened files.
3. Condition added to check whether the file is successfully opened or not.
4. If the file is successfully opened then start the stream of the opened file using while loop and storing each line of opened file.
5. Then, printed each line of the opened file.
6. When streaming of the opened file is completed they close the opened file using fclose() function.