Thread: Help on reading from a file.

I am trying to write a program (in C) for reading grid1.dat and grid2.dat and displays the data it has read on the screen.

I have got as far as the program listed below, it seems to compile fine but doesn’t seem to read correctly as most of the time a runtime error occurs. I’m also unsure how to implement the fprintf statement to get the data to be displayed on the screen.

Any help or advice would be greatly appreciated.

Many thanks

James.


Info stored in grid1.dat:

id x y
1 1.2 0.8
2 1.2 1.0
3 1.2 1.2
4 1.4 0.8
5 1.4 1.0
6 1.4 1.2
7 1.6 0.8
8 1.6 1.0
9 1.6 1.2


Info stored in grid2.dat:

id x y
1 1.2 0.8
2 1.2 1.0
3 1.2 1.2
4 1.4 0.8
5 1.4 1.0
6 1.4 1.2
7 1.6 0.8
8 1.6 1.0
9 1.6 1.2
10 1.8 0.8
11 1.8 1.0
12 1.8 1.2

Code:

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

int main(void)
{
char line[101], filename[101];
char*line_ptr;
struct node
	{
	int id;
	double x, y;
	};
struct node node_array[100];
int no_nodes = 0, no_values;
FILE*input_stream;
fprintf(stdout, "Enter file name:");
fscanf(stdin, "%s", filename);
if ((input_stream = fopen(filename, "r")) !=NULL)
	{
	fgets(line, sizeof(line), input_stream);
	while(((line_ptr = fgets(line, sizeof(line), input_stream)) !=NULL)&&
		  ((no_values = sscanf(line, "%d %lf %lf",
							   &node_array [no_nodes].id,
							   &node_array [no_nodes].x,
							   &node_array [no_nodes].y)) = =3)) no_nodes++;


if ((line_ptr !=NULL)&&(no_values !=3))
	fprintf(stdout, "Error reading line %s\n", line);
else
	if(line_ptr= =NULL)
	   fprintf(stdout, "End of file found\n");
}
}

hi,

i think i have solved ur problem. ur problem if i have understood is how to use fprintf in ur code. it is very simple buddy just some kind of a logic is required and u can do it......

ur whole code goes like this..............

Code:

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

int main(void)
{
	char line[101], filename[101];
	char*line_ptr;
	struct node
	{
		int id;
			double x, y;
	};
	
	struct node node_array[100];
	int no_nodes = 0, no_values=0;
	FILE*input_stream;

	fprintf(stdout, "Enter file name:");
	fscanf(stdin, "%s", filename);

	if ((input_stream = fopen(filename, "r")) !=NULL)
	{
		fgets(line, sizeof(line), input_stream);
		while((line_ptr = fgets(line, sizeof(line), input_stream))!=NULL)
        {
          if((no_values = sscanf(line, "%d %lf %lf",&node_array [no_nodes].id,&node_array [no_nodes].x,&node_array [no_nodes].y))==3)
          {
               no_nodes++;
          }
          if ((line_ptr !=NULL)&&(no_values !=3))
            fprintf(stdout, "Error reading line %s\n", line);
          else if(line_ptr==NULL)
	           fprintf(stdout, "End of file found\n");
          else
              fprintf(stdout,"%d %lf %lf\n",node_array [no_nodes-1].id,node_array [no_nodes-1].x,node_array [no_nodes-1].y);
        }
    }
    system("pause");
}

i think this will work for u and hope i i have solved ur problem sucessfully

bye
Praveen