Question

Write a C program to display the contents of the file in reverse order also copy the contents from one file to another file Your input and output must look something like this input to reverse function:
My Captain
output:
niatpaC yM

Answer 1

Initialise previous length of the text as 0.

Find the length of the current line and add it to the previous length. This given the next starting index of the new line.

Repeat the above steps till the end of the file.

Initialise the array of length of the given message in the given file.

Now rewind your file pointer and place the last pointer of the text to arr[K – 1] where K is the length of the array using fseek().

Print the length of the last line and decrease K by 1 for printing the next last line of the file.

Repeat the above steps untill K is equals to 0.

Below is the implementation of the above approach:

// C program for the above approach

#include <stdio.h>

#include <string.h>

#define MAX 100

// Function to reverse the file content

void reverseContent(char* x)

{

// Opening the path entered by user

FILE* fp = fopen(x, "a+");

// If file is not found then return

if (fp == NULL) {

printf("Unable to open file\n");

return;

}

// To store the content

char buf[100];

int a[MAX], s = 0, c = 0, l;

// Explicitly inserting a newline

// at the end, so that o/p doesn't

// get effected.

fprintf(fp, " \n");

rewind(fp);

// Adding current length so far +

// previous length of a line in

// array such that we have starting

// indices of upcoming lines

while (!feof(fp)) {

fgets(buf, sizeof(buf), fp);

l = strlen(buf);

a = s += l;

}

// Move the pointer back to 0th index

rewind(fp);

c -= 1;

// Print the contents

while (c >= 0) {

hope this will help you