Thread: Struct File and array problem Please help

Anyone knows why this code isn't working. the problem seems to be related to the size of the char arrays.

I am trying to read some data into a struct, write the struct to a file, close the file, read the data again and print it.

when I read and print the data again, it displays a lot of garbage characters.

Code:

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


struct clientInfo
{

	char name[25];
	char address[25];
	char telNumber[25];
	char attentionItem [25];
	char problemDescription[5];

};


int main()
{

	int i;
	const int size = 2;
	struct clientInfo data[size];
   struct clientInfo dat;
   FILE *clientFile;

   clientFile = fopen("clients.txt","w");

	for (i = 0; i < size; i++)
	{
      fflush(stdin);

		printf ("Please enter your name\n");
      gets (data[i].name);
		fflush(stdin);
		printf ("Please enter your address\n");
		gets (data[i].address);
		fflush(stdin);
		printf ("Please enter your telephone number\n");
		gets (data[i].telNumber);
		fflush(stdin);
		printf ("Please enter the item which aquires attention\n");
		gets (data[i].attentionItem);
		fflush(stdin);
		printf ("Please enter a description of the problem\n");
		gets (data[i].problemDescription);
		fflush(stdin);

   	fflush(stdin);
      fwrite(*data[i],sizeof(data[i]),1,clientFile);

   }//endfor

   fclose(clientFile);

   clientFile = fopen("clients.txt","r");

   while(!feof(clientFile))
   {
   	fread(&dat,sizeof(clientInfo),1,clientFile);

   	printf("name is %s\n",dat.name);
   	printf("address is %s\n",dat.address);
   	printf("telephone is %s\n",dat.telNumber);
      printf("attention is %s\n",dat.attentionItem);
   	printf("problem is %s\n",dat.problemDescription);

   }//end while

   fclose(clientFile);

   system("pause");

   return 0;

}//endmain

You're mixing your output and input modes.

Use fprintf() for text mode, and you can use fscanf(), (or any other text mode file reader), to read the data back into your program.

Use fwrite() to write out data in binary mode, and use fread() to read it back into your program.

It's always good to be specific when you open files:

Not just mode "r" for reading. Either "rt" or "rb", please. Be specific, either text or binary. Don't leave it up to some global variable buried in a header file, somewhere.

On what compiler do you get an error with file mode "rt"?

I use three compilers and have not noticed any problem with it.

Surprised that the compiler did not barf when it came across *data[i] as in.

Code:

fwrite(*data[i],sizeof(data[i]),1,clientFile); /* first arg should be a void pointer */

Instead of testing for feof() on the stream, a better test is to terminate if no. of items read is less than requested.

Code:

while(!feof(clientFile))  ???

it should be &data[i] and not *data[i] * I had changed it while attempting to debug the program. program seems to be fine. if I make all thee arrays sizes small. but gives problems when the array sizes are too large.

I really would like to continue using fwrite and gets.

gets because the name and address plus some other fields need to accept spaces.
fwrite because the struct is much larger than in the code I cut it down to help focus on the problem. And I do not want to have to use individual fprintf and fscanf statements for each field in the struct. Additionally I think fprintf and fscanf has problems with reading and writing spaces.

The first field is always fine. I might end up with a problem on the secord third fourth or fifth to the last field.

Thanks for all the replies

I read the faq's that vart suggested on fflush, feof, and fgets. I made the necessary changes I also am now reading in binary mode. the only effect now is that it is ony printing three characters from the string.

Code:

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

#define size 2

struct clientInfo
{

	char name[25];
	char address[25];
	char telNumber[25];
	char attentionItem [25];
	char problemDescription[6];

};


int main()
{

	int i,ch;
	struct clientInfo data[size];
   struct clientInfo dat;
   FILE *clientFile;

   clientFile = fopen("clients.txt","wb");

	for (i = 0; i < size; i++)
	{

		printf ("Please enter your name\n");
      fgets (data[i].name,sizeof(sizeof(char) * 25),stdin);
		//fflush(stdin);
      while ((ch = getchar()) != '\n' && ch != EOF);
		printf ("Please enter your address\n");
		fgets (data[i].address,sizeof(sizeof(char) * 25),stdin);
		//fflush(stdin);
      while ((ch = getchar()) != '\n' && ch != EOF);
		printf ("Please enter your telephone number\n");
		fgets (data[i].telNumber,sizeof(sizeof(char) * 25),stdin);
		//fflush(stdin);
      while ((ch = getchar()) != '\n' && ch != EOF);
		printf ("Please enter the item which aquires attention\n");
		fgets (data[i].attentionItem,sizeof(sizeof(char) * 25),stdin);
      while ((ch = getchar()) != '\n' && ch != EOF);
		//fflush(stdin);
		printf ("Please enter a description of the problem\n");
		fgets (data[i].problemDescription,sizeof(sizeof(char) * 6),stdin);
      while ((ch = getchar()) != '\n' && ch != EOF);

      fwrite(&data[i],sizeof(data[i]),1,clientFile);

   }//endfor

   fclose(clientFile);

   clientFile = fopen("clients.txt","rb");

   while(fread(&dat,sizeof(struct clientInfo),1,clientFile) != 0)
   {
   	printf("name is %s\n",dat.name);
   	printf("address is %s\n",dat.address);
   	printf("telephone is %s\n",dat.telNumber);
      printf("attention is %s\n",dat.attentionItem);
   	printf("problem is %s\n",dat.problemDescription);

   }//end while

   fclose(clientFile);

   system("pause");

   return 0;

}//endmain

Why is it only printing three characters from each string

for example if I entered Michelle for a name it gives me "Mic" only

Thanks in advance

Code:

	
PHP Code:
	

#define size 2 



you only allow it too using fgets this way.

	
PHP Code:
	

for (i = 0; i < size; i++)
    {

        printf ("Please enter your name\n");
      fgets (data[i].name,sizeof(sizeof(char) * 25),stdin); 



here is how i use fgets and i am not sure if am doing it right either but it reads the specified max input and prints it out.

	
PHP Code:
	

#include <stdio.h>

int main(int argc, char** argv)
{
    char str[200];
     
    fgets(str,(sizeof str),stdin);
         printf("%s\n",str);    
    return 0;
} 



you have only allowed it to read the defined 2 bytes as maxsize plus the extra character from the increment of i++ .also 

	
PHP Code:
	

 (sizeof char 



) is one byte exactly. 
hope it helps. i am newbie and i have really bad eyesight so apology if i missed anything or made any mistakes.

The reason for the while loop is to clean out the input stream as suggested in the faq instead of using fflush(stdin) however I removed them and the code still works.

Thanks a lot to everyone
Thanks vart for making me read the faqs they were very enlightening.
cmay your suggestion finally got my code working.

ItCbitC thanks for all your suggestion.

Thanks a lot I can't say thanks enough to you guys.

Here is the modified and working code

Code:

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

#define size 2

struct clientInfo
{

	char name[25];
	char address[25];
	char telNumber[25];
	char attentionItem [25];
	char problemDescription[200];

};


int main()
{

	int i;
	struct clientInfo data[size];
   struct clientInfo dat;
   FILE *clientFile;

   clientFile = fopen("clients.txt","wb");

	for (i = 0; i < size; i++)
	{

		printf ("Please enter your name\n");
      fgets (data[i].name,sizeof(data[i].name),stdin);

		printf ("Please enter your address\n");
		fgets (data[i].address,sizeof(data[i].name),stdin);

		printf ("Please enter your telephone number\n");
		fgets (data[i].telNumber,sizeof(data[i].name),stdin);

		printf ("Please enter the item which aquires attention\n");
		fgets (data[i].attentionItem,sizeof(data[i].name),stdin);

      printf ("Please enter a description of the problem\n");
		fgets (data[i].problemDescription,sizeof(data[i].name),stdin);

      //write information to file
      fwrite(&data[i],sizeof(data[i]),1,clientFile);

   }//endfor

   fclose(clientFile);

   clientFile = fopen("clients.txt","rb");

   while(fread(&dat,sizeof(struct clientInfo),1,clientFile) == 1)
   {
   	printf("name is %s\n",dat.name);
   	printf("address is %s\n",dat.address);
   	printf("telephone is %s\n",dat.telNumber);
      printf("attention is %s\n",dat.attentionItem);
   	printf("problem is %s\n",dat.problemDescription);

   }//end while

   fclose(clientFile);

   system("pause");

   return 0;

}//end main