Thread: Skipping to a new line in an input file.

1. Read in entire lines of data from the file into a buffer using the fgets function.
2. Use the sscanf function to just parse the first six fields from the line you just read in.
3. Repeat as necessary.

Code:

#include <stdio.h>

struct EDFSection
{
   char Param[20];
   int Label, SFactor, SigBits, Bit30, Bit31;
};

int main()
{
   static const char filename[] = "file.txt";
   FILE *file = fopen(filename, "r");
   if ( file != NULL )
   {
      char line[80];
      while ( fgets(line, sizeof line, file) != NULL )
      {
         struct EDFSection Sec;
         if ( sscanf(line, "%s %d %d %d %d %d", Sec.Param, &Sec.Label,
                     &Sec.SFactor, &Sec.SigBits, &Sec.Bit30, &Sec.Bit31) == 6 )
         {
            printf("Sec.Param   = %s\n", Sec.Param);
            printf("Sec.Label   = %d\n", Sec.Label);
            printf("Sec.SFactor = %d\n", Sec.SFactor);
            printf("Sec.SigBits = %d\n", Sec.SigBits);
            printf("Sec.Bit30   = %d\n", Sec.Bit30);
            printf("Sec.Bit31   = %d\n", Sec.Bit31);
            putchar('\n');
         }
      }
      fclose(file);
   }
   return 0;
}

/* my output
section.Param   = month
section.Label   = 1
section.SFactor = 3
section.SigBits = 4
section.Bit30   = 5
section.Bit31   = 6

section.Param   = day
section.Label   = 2
section.SFactor = 5
section.SigBits = 5
section.Bit30   = 66
section.Bit31   = 7
*/

Code:

      while ( fgets(line, sizeof line, file) != NULL )
      {
         struct EDFSection Sec;
         if ( strncmp(line, "ENDL", 4) == 0 )
         {
            break;
         }
         if ( strncmp(line, "END", 3) != 0 &&
              sscanf(line, "%s %d %d %d %d %d", Sec.Param, &Sec.Label,
                     &Sec.SFactor, &Sec.SigBits, &Sec.Bit30, &Sec.Bit31) == 6 )
         {
            /* printing */
         }
      }
      fclose(file);

http://www.rt.com/man/fgets.3.html

but it doesn't like it.
it exits the loop right away.

Well of course it does, silly!

Code:

if (strncmp(line, "ENDL", 4))
			break;

Notice anything missing here?!


Quzah.

I thought

Code:

strncmp(line, "ENDL", 4)

returns a 1 when the strings are the same. Never mind then.

Instead of printing out the structure every time I scan it, I want to store then in an array of structures. So I'd pass the pointer to the array to a function that will read in all the individual structures. I don't really get how it is explained here:

Code:

struct Node *make_node ( void )
{
  struct Node new_node = malloc ( sizeof *new_node );

  /* Error check and set a default state */

  return new_node;
}

That's from Prelude's FAQ again.

I did it like it makes sense to me:

Code:

int 
main (void)
{
	int i, j, nExpected, nActual=0;
	char Word[25]; 
	FILE* inp;
	struct EDFLine *Sec;
..........................
Sec = calloc(nExpected, sizeof (struct EDFLine));

	ReadSection(inp, Sec, nExpected, &nActual);
}

int ReadSection(FILE * inp, struct EDFLine Sec[], int nExpected, int*nActual)
{
	char line[80];
	int  i=0;

	while ( fgets(line, sizeof line, inp) != NULL )
	{
		if ( strncmp(line, "ENDL", 4) == 0 )
		{
            break;
         }

		if (strncmp(line, "END", 3) != 0)
		{
			if ( sscanf(line, "%s %d %d %d %d %d", Sec[i].Param, &Sec[i].Label,
                     &Sec[i].SFactor, &Sec[i].SigBits, &Sec[i].Bit30, &Sec[i].Bit31) == 6)
			{
				nActual ++;
				i++;
			}
		}
		
	}

	if (*nActual == nExpected)
		return 1;
	else 
		return 0;
}

Right now it exits the loop right away, again.

Oh, and you guys told me numerously before not to typecast the calloc and never worked for me before. It kept giving me an incompatibility error, but now it worked.....

Oh, and you guys told me numerously before not to typecast the calloc and never worked for me before. It kept giving me an incompatibility error,

That's because you were compiling as C++ instead of C.


Quzah.

Originally Posted by earth_angel

Instead of printing out the structure every time I scan it, I want to store then in an array of structures.

How about something along this line?

Code:

size_t EDFread(const char *filename, struct EDFSection Sec[], size_t size)
{
   size_t i = 0;
   FILE *file = fopen(filename, "r");
   if ( file != NULL )
   {
      char line[80];
      while ( fgets(line, sizeof line, file) != NULL )
      {
         static const char stop[] = "ENDL", ignore[] = "END";
         if ( strncmp(line, stop, sizeof stop - 1) == 0 )
         {
            break;
         }
         if ( strncmp(line, ignore, sizeof ignore - 1) != 0 &&
              sscanf(line, "%s %d %d %d %d %d", Sec[i].Param,
                     &Sec[i].Label, &Sec[i].SFactor, &Sec[i].SigBits,
                     &Sec[i].Bit30, &Sec[i].Bit31) == 6 )
         {
            if ( ++i >= size )
            {
               break;
            }
         }
      }
      fclose(file);
   }
   return i;
}

int main()
{
   struct EDFSection section[10];
   size_t size = EDFread("file.txt", section, sizeof section / sizeof *section);
   /* ... */
   return 0;
}

struct EDFSection section[10];

That works, but the size of the array is not always 10. I have to dynamically allocate memory. So I end up passing to the function a pointer to an array of structures dynamically allocated. That's where the problems begin. I'm not sure how to arrange that.

What is size_t?

Originally Posted by earth_angel

That works, but the size of the array is not always 10. I have to dynamically allocate memory. So I end up passing to the function a pointer to an array of structures dynamically allocated. That's where the problems begin. I'm not sure how to arrange that.

Code:

int main()
{
   size_t size = 10;
   struct EDFSection *section = malloc(size * sizeof *section);
   if ( section )
   {
      size_t count = EDFread("file.txt", section, size);
      /* ... */
      free(section);
   }
   return 0;
}

Originally Posted by earth_angel

What is size_t?

An unsigned integral type suited for array indexing.

Print the structure after a line is successfully read and before you increment the index.