Unlocking the Power of File Handling in C Programming

The Problem Statement

Imagine you have a file named program.txt containing a text message in the current directory. Your task is to create a program that reads the first line from this file and saves its content to a string until a newline character (\n) is encountered.

The Solution

To tackle this challenge, you’ll need to possess knowledge of C file handling and string programming concepts. The program will open the program.txt file and read its content character by character, storing it in a string until a newline character is detected.

The Code

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fp;
    char c, str[100];

    fp = fopen("program.txt", "r");
    if (fp == NULL) {
        printf("Error: File not found\n");
        exit(1);
    }

    int i = 0;
    while ((c = fgetc(fp))!= '\n' && c!= EOF) {
        str[i++] = c;
    }
    str[i] = '\0';

    printf("First line: %s\n", str);

    fclose(fp);
    return 0;
}

How it Works

Let’s break down the code step by step:

• We open the program.txt file in read mode (“r“).
• If the file is not found, an error message is printed, and the program terminates.
• We create a character array str to store the first line of the file.
• The while loop reads characters from the file until a newline character or the end of the file is reached, storing each character in the str array.
• Finally, we print the first line and close the file.

The Output

If the program.txt file contains the following text:

This is the first line.
This is the second line.

The program’s output will be:

First line: This is the first line.

On the other hand, if the file is not found, the program will print:

Error: File not found