Program to append file in C

Algorithm

Let's first see what should be the step-by-step procedure to compare two integers−

START
      
   Step 1 → Take two integer variables, say A & B
          
   Step 2 → Assign values to variables

   Step 3 → Compare variables if A is greater than B
   
   Step 4 → If true print A is greater than B
   
   Step 5 → If false print A is not greater than B

STOP

Flow Diagram

We can draw a flow diagram for this program as given below −

Pseudocode

Let's now see the pseudocode of this algorithm −

procedure compare(A, B)

   IF A is greater than B
      DISPLAY "A is greater than B"
   ELSE
      DISPLAY "A is not greater than B"
   END IF
      
end procedure

Implementation

Assuming we have file with name file_append.txt with this content −

This text was already there in the file.

Now, we shall see the actual implementation of the program −

#include <stdio.h>
 
int main()
{
   FILE *fp;
   char ch;
   char *filename = "file_append.txt";
   char *content = "This text is appeneded later to the file, using C programming.";

   /*  open for writing */
   fp = fopen(filename, "r");
   
   printf("\nContents of %s  -\n\n", filename);
   
   while ((ch = fgetc(fp) )!= EOF)
   {
      printf ("%c", ch);
   }

   fclose(fp);
   
   fp = fopen(filename, "a");

   /* Write content to file */
   fprintf(fp, "%s\n", content);

   fclose(fp);

   fp = fopen(filename, "r");

   printf("\nContents of %s  -\n", filename);
   
   while ((ch = fgetc(fp) )!= EOF)
   {
      printf ("%c", ch);
   }

   fclose(fp);

   return 0;
}

Output

Output of this program should be −

Contents of file_append.txt  -
This text was already there in the file.

Appending content to file_append.txt...

Content of file_append.txt after 'append' operation is -

This text was already there in the file.
This text is appeneded later to the file, using C programming.