file input/output

[Raison]

I am suppose to write a program that can save a list of names and its relevant info(into a structure). However, i have problem retrieving the "name" datas out when i open the program again.Here's a summary of what i wrote.PLEASE TAKE NOTE OF LINE A AND LINE B.

/* structure declaration */
typedef struct {
				char marker;
				char id;
				char name[21];
			
			}data;
/* function protype */
void quit(data seat[12]);

main(void)
{


/* declare variables */
	data seat[12];
	int seatId, i,choice, num_Seat=0;

	/* file pointers for marker,id and name respectively */
	FILE *fpM, *fpID, *fpName;
	
		
	/* load data from data file */
	fpM = fopen("markerData", "rt");
	fpID = fopen("idData","rt");
	fpName = fopen("nameData","rt");


	if ((fpM == NULL) || (fpID == NULL) || (fpName == NULL))
	{printf("Error in loading data.\n");
		
	return 0;}


	for (i=0;i<12;i++)
	{
			seat[i].id = fgetc(fpID);
		
			seat[i].marker = fgetc(fpM); 

			/* LINE A */
			fscanf(fpName,"%s",seat[i].name);
					
		
			
			
	  }


	fclose(fpM);
	fclose(fpID);
	fclose(fpName);
	

.............
/*
 the main() receives inputs from user and managed to store them successfully in the array structure seat[12]. Then, the program quits and saves the data by calling quit().
*/


}


void quit(data seat[12])
{
	
	int i;
	FILE *fpM, *fpID, *fpName;


		
	fpM = fopen("markerData", "wt");
	fpID = fopen("idData","wt");
	fpName = fopen("nameData","wt");
	printf("Quiting....\n");
	if ((fpM == NULL) || (fpID == NULL) || (fpName == NULL))
	{printf("Error in saving data.\n");
	return ;}
	
	
	/* saving data */
	for (i=0;i<12;i++)
	{
	fprintf(fpM,"%c",seat[i].marker);
	
	fprintf(fpID,"%c",i+1);
	
                 /* LINE B */
	fprintf(fpName,"%s",seat[i].name);

		}

	fclose(fpM);
	fclose(fpID);
	fclose(fpName);

}

My program cannot retrieve the datas from seat[i].name properly.
Strange characters are stored inside seat[i].name instead of what i intend.

 


However, if i changed the 
line a:
fscanf(fpName,"%s",seat[i].name);
 
to 

fscanf(fpName,"%s\n",seat[i].name);


AND

line b:
fprintf(fpName,"%s",seat[i].name);

to 

fprintf(fpName,"%s\n",seat[i].name);


My program will be able to retrieve the datas out properly.

Can someone tell me why is it necessary to add the newline character? As i write each string into the file *fpName using fprintf(), is the NULL character added? Somehow i think my fscanf() doesnt recognise any NULL character during the loading at line a. That's why i couldnt retrieve the names out.

[Dave_Sinkula]

>Can someone tell me why is it necessary to add the newline character?

To separate the strings with whitespace.

>As i write each string into the file *fpName using fprintf(), is the NULL character added?

No.

By the way, NULL is a macro which expands to an implementation-defined null pointer constant. A null character is byte with all bits set to 0, used to terminate a character string.

>Somehow i think my fscanf() doesnt recognise any NULL character during the loading at line a. That's why i couldnt retrieve the names out.

It sounds to me like strings may have been concatenated together. For example, "Bob", "Bill", and "Jim" were written as "BobBillJim".

I don't think the \n is necessary in the call to fscanf because strings are whitespace-delimited.
http://www.eskimo.com/~scs/C-faq/q12.17.html

[Raison]

If i manage to write my strings of name with a NULL character at each of the names(so that they r not contenated), will fscanf() recognise each NULL character and seperate the strings into different array(i.e seat[i].name) or the only way is to separate the strings with a whitespace character?

If it is possible, how do i write the strings with the NULL characters added to the file?

[Dave_Sinkula]

>NULL character

Please reread what I wrote about the terminology.

>If it is possible, how do i write the strings with the NULL characters added to the file?

I added a null character to the end of the string this way.

#include <stdio.h>
int main(void)
{
   const char filename[] = "file.txt";
   FILE *file = fopen(filename, "w");
   if ( file )
   {
      const char *text[] = { "The", "quick", "brown", "dog"};
      size_t i;
      for ( i = 0; i < sizeof text / sizeof *text; ++i )
      {
         fprintf(file, "%s", text[i]);
         fputc('\0', file);
      }
      fclose(file);
   }
   return 0;
}

>If i manage to write my strings of name with a NULL character at each of the names(so that they r not contenated), will fscanf() recognise each NULL character and seperate the strings into different array(i.e seat[i].name) or the only way is to separate the strings with a whitespace character?

In a simple test I tried, I think not.

#include <stdio.h>
int main(void)
{
   const char filename[] = "file.txt";
   FILE *file = fopen(filename, "r");
   if ( file )
   {
      char buffer[BUFSIZ];
      while ( fscanf(file, "%s", buffer) == 1 )
      {
         printf("buffer = \"%s\"\n", buffer);
      }
      fclose(file);
   }
   return 0;
}

But that may be because the %s directive "[m]atches a sequence of non-white-space characters", and I don't believe a null character is considered white-space.

white-space characters (space, horizontal tab, new-line, vertical tab, and form-feed)