Thread: Writing to a file

I'd like to input the values that I compute, in a loop, to a file that I've already read from. I've opened it as a read/write file. I can't seem to make it work, though it looks as if it should. Any ideas?

Code:

#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
#define L1 1000
#define L2 1000


void eliminateEnters (char s1[]);
void DetermineAngle( struct Scara * );
void CalcMotorPulses ( struct Scara *s );
double CheckSum ( struct Scara *s );


struct Scara
{
	char name[256];
	double x;
	double y;
	double z;
	double joint1;
	double joint2;
	double joint3;
	int motor1;
	int motor2;
	int motor3;
	double checkSum;
};

FILE *in;

void main()
{
	char fileStr[30];
	char buffer[256];
	int i;
	int j;
	int p;
	struct Scara pts[10];
	double sum;
	
	printf("\nPlease enter the name of the file that you'd like to read points from: ");
	gets(fileStr);

	in = fopen(fileStr, "a+");

	if (in == NULL)
	{
		printf("\nFile Error......");
		exit(1);
	}

	printf("\n%s openend for reading", fileStr);

	/*fprintf(in,"\nX-pt  Y-pt   Z-pt  Joint1  Joint2  Joint3  Motor1  Motor2  Motor3  CheckSum");
	fprintf(in,"\n===   ===    ===   =====   =====   =====   =====   =====   =====   ========");*/
	printf("\n\nX-pt  Y-pt   Z-pt  Joint1  Joint2  Joint3  Motor1  Motor2  Motor3  CheckSum");
	printf("\n===   ===    ===   =====   =====   =====   =====   =====   =====   ========");
	
	j=0;

	while(j<10)
	{
		i=0;
		while( (fgets(buffer, 256, in) != NULL) )
		{
			eliminateEnters(buffer);
			if(i == 0)
				strcpy(pts[j].name, buffer);
			if(i == 1)
				pts[j].x = atof(buffer);
			if(i == 2)
				pts[j].y = atof(buffer);
			if(i == 3)
				pts[j].z = atof(buffer);
			//printf( "i=%d, buffer=%s\n", i, buffer );
    		i++;
			if ( i > 3 )
				break;
		}
	DetermineAngle(&pts[j]);
	CalcMotorPulses (&pts[j]);
	sum = CheckSum (&pts[j]);
	printf("\n\n%5.2lf %5.2lf%5.2lf  %5.2lf  %5.2lf  %5.2lf   %3d  %3d   %3d    %5.2lf", pts[j].x, pts[j].y, pts[j].z, pts[j].joint1, pts[j].joint2, pts[j].joint3, pts[j].motor1, pts[j].motor2, pts[j].motor3, sum);
	//fprintf(in,"%5.2lf %5.2lf%5.2lf  %5.2lf  %5.2lf  %5.2lf   %3d  %3d   %3d    %5.2lf", pts[j].x, pts[j].y, pts[j].z, pts[j].joint1, pts[j].joint2, pts[j].joint3, pts[j].motor1, pts[j].motor2, pts[j].motor3, sum);
	j++;
	}

	for(p=0;p<10;p++);
	fprintf(in,"%5.2lf %5.2lf%5.2lf  %5.2lf  %5.2lf  %5.2lf   %3d  %3d   %3d    %5.2lf", pts[p].x, pts[p].y, pts[p].z, pts[p].joint1, pts[p].joint2, pts[p].joint3, pts[p].motor1, pts[p].motor2, pts[p].motor3, sum);

	





}

/*********************************************************************
*	Name: eliminateEnters
*	About: eliminates enters from an array so that only numbers, periods, or the NULL character occurs
*	Arguments (character array)
*	Returns (none)
*********************************************************************/
void eliminateEnters (char s1[])
{
	int i=1;
	
	while(s1[i] != '\0')
	{
		if(s1[i] == '\n')
			s1[i] = '\0';
	i++;
	}
}

#include <math.h>

void DetermineAngle( struct Scara *s )
{
	double B, Beta, anglealpha, Angleone, Angletwo;

	B = sqrt((s->x * s->x)+(s->y * s->y));
	Beta = atan2(s->y,s->x);
	anglealpha = acos(((L2*L2) - (B*B) - (L1*L1))/ (-2*B*L1));
	Angleone = Beta + anglealpha;
	Angletwo = atan2((s->y-(350*sin(Angleone))),(s->x-(350*cos(Angleone))));

	(s->joint1 = Angleone * (180/3.1416));
	(s->joint2 = Angletwo * (180/3.1416));
	(s->joint3 = s->z);
}

void CalcMotorPulses ( struct Scara *s )
{
	s->motor1 = s->joint1 * 800;
	s->motor2 = s->joint2 * 800;
	s->motor3 = s->joint3 * 400;

	if(s->motor1 < 0)
		s->motor1 = s->joint1 * 800 * -1;

	if(s->motor2 < 0)
		s->motor2 = s->joint2 * 800 * -1;

	if(s->motor3 < 0)
		s->motor3 = s->joint3 * 400 * -1;
}

double CheckSum ( struct Scara *s )
{
	return ( (s->joint1)+(s->joint2)+(s->joint3)+(s->motor1)+(s->motor2)+(s->motor3)+(s->x)+(s->y)+(s->z) );
}

Thanks for the help on previous posts. I figured this one out on my own. Good luck programming.