Error-Handling functions in C

Function clearerr ()

The function prototype is as given below.

void(clearerr(FILE* Stream);

The function clears the end of file and error indicator for the argument stream

Function feof ()

The function prototype for this function is written in the following manner:

int feof(FILE*Stream);

The function finds if the EOF indicator is set for the stream pointed to by the argument. If so, it returns a non-zero value.

Function ferror ()

The function prototype is written as shown below.

int ferror(FILE*stream);

The function finds the status of error indicator with the stream. The function returns zero if there is no error, otherwise returns a non-zero value. The function perror () may be used to find the type of the error.

Function perror ()

The function prototype is written as given below.

void perror(const char* str);

The function displays a string giving error message as predefined in compiler for a particular error condition.

Illustrates functions feof (), clearerr (),and ferror ()

#include <stdio.h> 
 #include <stdlib.h> // for exit function 
 void main() 
 { 
   FILE* Fptr; 
   int i, j, k[6]; 
   Fptr = fopen("file1","w"); 
   clrscr(); 
   if (Fptr ==NULL) 
   { 
      printf("File could not be opened."); 
      exit(1); 
   } 
   else 
      fprintf(stdout, "File is open. Enter data.\n"); 
      for(i =0; i <6; i++) 
      putw( k [i] = 5*i, Fptr ); 
      fclose(Fptr); 
      Fptr = fopen ("file1","r"); 
      printf("The values of elements of array k are as below.\n"); 
      for (j =0; j<7; j++) 
      printf("%d\t", getw(Fptr)); 
      printf ("\n"); 
      if (feof(Fptr)) 
                   printf("File end has occurred.\nfeof = %d\n", feof(Fptr)); 
             else 
                   printf("File end has not occurred.\nfeof = %d\n", feof(Fptr) ); 
                   printf("ferror = %d\n", ferror(Fptr)); 
                   printf("After clearerr action.\n"); 
                   clearerr(Fptr); 
                   if(feof(Fptr)) 
                       printf("File end has occurred. \nAnd feof = %d\n", feof(Fptr)); 
                   else 
                       printf("File end has not occurred.\nAnd feof = %d\n",feof(Fptr)); 
                       printf("ferror = %d\n", ferror(Fptr)); 
                       fclose(Fptr); 
 }