fgets error handling

**mlsbbe** · 03-23-2003

Does anybody know why my code for error handling in fgets doesn't work? I've been trying to make this work for ages, and still cannot get this to work. What happens is that instead of skipping the line:

Code:

printf("\nInput line too long for buffer\n")

when p_str!=NULL, it prints the string out as well.

Thanks in advance.
Below part of my code (though not all of it):

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define MAXSTUDENT 40
#define MAXNAME 20

/*Declaring Function Prototypes*/
int extract (char *copy_str, char *name_str, int length, student_t *s,int *p_index); 

int main(void)
{                 
FILE *readfile;
char str_copy[40];
char str_name[MAXNAME+1];
char *p_str;
int i;                           

student_t s [MAXSTUDENT]; 
int num=0; 
int result,index;
char *p_error;

                              
if((readfile=fopen("datafile.txt","rt"))==NULL)
{
printf("Error, unable to read file.  Program exiting");
return (1);
}else
 {
 
 for(index=0;((p_error=fgets(str_copy,sizeof(str_copy),readfile))!=NULL);index++)
        
                {
                        if((p_str=strchr(str_copy,'\n'))!=NULL)
                                {
                                *p_str='\0'; /*fgets may not read \n, because data might me overwritten*/
                                result=extract(str_copy,str_name,MAXNAME,s,&index);
                        
                                } else
        
                                {
                                printf("\nInput line too long for buffer\n"); //This line is printed out when p_str!=NULL

                                exit(0);
                                }
                }
 

 if(p_error==NULL){
  printf("Error in reading file"); /*EOF error*/
  }

}        


fclose(readfile);

return (0);
}

**Prelude** · 03-24-2003

I don't see a problem. When the buffer is filled and no newline is read, the error message is printed and the program terminates. Otherwise extract is called.

-Prelude

**mlsbbe** · 03-24-2003

I've remade the file so that now I can compile it. However, this time, it doesn't skip out the line

Code:

if (p_error==NULL)
  {  
  printf("\nError in reading file"); /*EOF error*/
  }

even when the following line condition is true:

Code:

while((p_error=fgets(str_copy,sizeof(str_copy),readfile))!=NULL)

Below is the code:

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define MAXSTUDENT 40
#define MAXNAME 20
 
typedef struct{
char name[MAXNAME+1];
int ex1,ex2,ex3,ex4,average;
}student_t;


int main(void)
{                 
FILE *readfile;
char str_copy[40];
char str_name[MAXNAME+1];
char *p_str;
int i,index;                           

student_t s [MAXSTUDENT]; 


char *p_error;

                              
if((readfile=fopen("results.txt","rt"))==NULL)
{
printf("Error, unable to read file.  Program exiting");
return (1);
}else
 {
 
  
                while((p_error=fgets(str_copy,sizeof(str_copy),readfile))!=NULL)
        
                {
                index=0;
                if((p_str=strchr(str_copy,'\n'))!=NULL)
                   
                   {
                   *p_str='\0';
                   printf("\nInput line OK");
                   } else
                        
                        {
                        printf("\nInput line too long for buffer\n"); 
                        exit(0);
                        }
                        
                index++;
                
                }
                
  if (p_error==NULL)
  {  
  printf("\nError in reading file"); /*EOF error*/
  }

}

fclose(readfile);
return (0);
}

Please Can somebody help me? I dunno why this doens't work.

**Hammer** · 03-24-2003

I can't see a need for this bit:

Code:

    if (p_error == NULL)
    {
      printf("\nError in reading file");  /*EOF error*/
    }

Also, I can't see or understand your problem. Can you try explaining it in more detail please...

**mlsbbe** · 03-24-2003

i've just started a new thread -
'File IO help please'
and i've explained my problem better I think. Thankyou for the help! T

**Hammer** · 03-24-2003

>>i've just started a new thread
Err. ok, I'll close this one. But please don't create unnecessary threads, we could have continued here.

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