#include <stdio.h>
#include <stdlib.h> // For exit() function
int main()
{
char c[1000];
FILE *fptr;
if ((fptr = fopen("program.txt", "r")) == NULL)
{
printf("Error! opening file");
// Program exits if file pointer returns NULL.
exit(1);
}
// reads text until newline
fscanf(fptr,"%[^\n]", c);
printf("Data from the file:\n%s", c);
fclose(fptr);
return 0;
}

If the file program.txt is not found, this program prints an error message.

If the file is found, the program saves the file’s content to a string c until the ‘\n’ newline is encountered.

Suppose, the program.txt file contains the following text.

C programming is awesome.
I love C programming.
How are you doing?

The output of the program will be:

Data from the file: C programming is awesome.

C program that reads a line from a file and displays it:

#include <stdio.h>

int main() {
    FILE *fp;
    char line[100];

    fp = fopen("file.txt", "r");

    if (fp) {
        fgets(line, 100, fp);
        printf("Line read from file: %s", line);
        fclose(fp);
    } else {
        printf("Failed to open file.\n");
    }

    return 0;
}

Explanation:

• #include <stdio.h> includes the standard input-output header file in our program, which provides input and output operations functionality.
• int main() is the entry point of our program.
• FILE *fp; declares a file pointer variable fp that will be used to open and read the file.
• char line[100]; says a character array line that will be used to store the line read from the file.
• fp = fopen("file.txt", "r"); opens the file named “file.txt” in read mode and assigns the file pointer to fp.
• if (fp) { ... } checks if the file was opened successfully. If the file was opened successfully, the code inside the curly braces is executed, otherwise, it is skipped.
• fgets(line, 100, fp); reads a line from the file using fgets() and stores it in the line array. fgets() reads at most 100 characters (including the newline character) from the file.
• printf("Line read from file: %s", line); prints the line read from the file to the console using printf().
• fclose(fp); closes the file.

When we compile and run this program, it will read the first line from the “file.txt” file and display it to the console.