Lab Exercises

1. Write a program to compare two files, printing the first line where they differ.
2. Write a program that, given two files exam1.dat and exam2.dat, appends the second file to the first.
3. Write a program that displays the contents of a file in reverse order.

Lab Solutions

1. Program that compares two files -
   

    #include <stdio.h>
   #include <string.h>
   void main()
   {
       char str1[251],str2[251];
       FILE *fp1, *fp2; 
       /* assume that two files, exam1.dat and exam2.dat exist already */
       fp1=fopen ("exam1.dat", "r"); 
       fp2=fopen ("exam2.dat", " r");
       while (fgets (str1,251, fp1) ! =NULL)
       {
           if (fgets (str2,251, fp2) ==NULL)
           {
               printf ("
   Exam1 is longer"); 
           break;
        }
        if (strcmp (strl, str2) !=0)
        {
            printf("
   The lines where they differ are");
            print f ("%s", str1); 
            printf ("%s", str2); 
            break;
         }
      }
      if (strcmp (strl, str2) ==0 && fgets (str2, 251, fp2)! =NULL)
      {
         print f ("
   Exam2 is longer"):	
         return;
       }
       if (strcmp (strl, str2) ==0) 
           printf ("
   The two files are equal");
       fclose (fp1) ;
       fclose ( fp2) ;
   }
   

   Run
2. Program that appends one file to another -
   

   #include <stdio.h> 
   void main()
   {
       char c;
       FILE *fp1, *fp2;
       /* assume that two files, exam1.dat and exam2.dat exist already */
       fp1 = fopen ("exam1.dat", "a");
       fp2 = fopen ("exam2.dat", "r");
       c=fgetc (fp2);
       while(c != EOF)
       {
          fputc (c, fp1);
          c=fgetc(fp2);
        }
        fclose (fp1); 
        fclose (fp2);
   }
   
   

   Run
3. Program that displays the contents of a file in reverse order -
   

   #include <stdio.h> 
   void main ()
   {
      char c; 
      long int pos;
      FILE *fp; 
      /* assume that a file, exam.dat exists already */ 
      fp = fopen ( "exam.dat", "r"); 
      pos = ftell (fp); 
      fseek ( fp, -1,2) ;
      while (ftell (fp) >pos) 
      {
         c=fgetc (fp); 
         fseek (fp, -2, 1) ; 
         printf ("%c", c); 
      }
      c=fgetc(fp);
      printf("%c", c); 
      fclose (fp) ;
   }
   

   Run