Question

我有一个程序需要从文件中读取数据，但我不想提供文件名，并且想要将数据存入我的命令文件，如nbody＆lt;输入???

我提供的代码（称为nbody.c）是N体仿真的简化版本，用于说明上述理论。可以使用以下命令编译，链接代码和名为nbody的可执行文件。 gcc -lm nbody.c -o nbody

为了运行可执行文件，提供了一个名为input的示例数据输入文件作为起点。可以使用以下命令执行串行代码，该命令需要几秒钟才能运行完成。 nbody＆lt;输入

我的节目是;

#include <stdio.h>
#include <math.h>

int m = 1000;
void simulate(int m, int n, double delt, double eps, double x[], double y[], double z[], 
              int iter, double xn[], double yn[], double zn[]);

int main(int argc, char *argv[])
{
double x[m], y[m], z[m], xn[m], yn[m], zn[m];
double delt, eps, resultant;
int i, n, iter;

char ch, file_name[25];

FILE *fp, *ofp;
//file_name=argv[0];
//char *mode = "r";

printf("Enter the name of file you wish to see\n"); //instead of this, i wanted it reads automatically, like taking data from the file and calculate it.

gets(file_name);
fp = fopen(file_name, "r");

rewind(fp);
printf("The contents of %s file are : \n", file_name);

 fscanf(fp,"%d  %lf  %lf", &n, &delt, &eps); 
   printf("n = %d, delta t = %lf and tolerance = %lf \n",n, delt, eps);

   fclose(fp);

//while(ch=fgets(fp)!=EOF){

//printf("enter n, delta t and tolerance\n");
//scanf("%d  %lf  %lf", &n, &delt, &eps);
//printf("%c",ch)


//printf("enter n, delta t and tolerance\n");
//scanf("%d  %lf  %lf", &n, &delt, &eps);



simulate(m, n, delt, eps, x, y, z, iter, xn, yn, zn);
printf("n = %d, delta t = %lf and tolerance = %lf \n",n, delt, eps);
for (i=1; i <= n; i++) {
   resultant = sqrt(x[i]*x[i]+y[i]*y[i]+z[i]*z[i]);
   printf("%-5.7lf  %-5.7lf  %-5.7lf  %-5.7lf\n", x[i], y[i], z[i], resultant);
   }
return 0;
}


void simulate(int m, int n, double delt, double eps, double x[], double y[], double z[], 
              int iter, double xn[], double yn[], double zn[])
{
/* 
Author C.Ierotheou
Aug 2009
Copyright University of Greenwich
routine to crudely simulate body-body interactions (inefficient method)
*/
double zero = 0.0, one = 1.0, twopi = 6.2831853071795864769252866;
int i, itest, j;
double aux,auy,delt2,delt3,eps2,fx,fy,fz,ftx,fty,ftz,step;

// return if n<5
if (n < 5) return;

//initialization
iter = 0;
delt2 = 0.5*delt*delt;
delt3 = delt2*delt2;
eps2 = eps*eps;

//initial distribution of points
auy = zero;
itest=n+1;
j = n+2;
fx = (double)(n);
x[1] = zero;
y[1] = zero;
z[1] = one;
for (i=2; i <= n; i++) {
   step = (double)(i+i-j)/fx;
   auy = fmod(auy+3.6/sqrt(itest*(one-step*step)),twopi);
   aux = sin(auy);
   x[i] = aux*step;
   y[i] = aux*sin(acos(step));
   z[i] = cos(auy);
   }

// main iteration loop

Mainloop:
   iter=iter+1;
   itest=0;
   for (i=1; i <= n; i++) {
      // total sum of force vectors
      fx=zero;
      fy=zero;
      fz=zero;
      for (j=1; j<=n ; j++) {
         if (j != i) {
            aux=pow(x[i]-x[j],2.0)+pow(y[i]-y[j],2.0)+pow(z[i]-z[j],2.0);
            aux=aux*sqrt(aux);
            fx=fx+(x[i]-x[j])/aux;
            fy=fy+(y[i]-y[j])/aux;
            fz=fz+(z[i]-z[j])/aux;
                }
         }
      // tangential component of force
      aux=x[i]*fx+y[i]*fy+z[i]*fz;
      ftx=fx-x[i]*aux;
      fty=fy-y[i]*aux;
      ftz=fz-z[i]*aux;
      aux=ftx*ftx+fty*fty+ftz*ftz;
      if (aux > eps2) {
         itest=1;
         aux=sqrt(one-aux*delt3);
         xn[i]=x[i]*aux+ftx*delt2;
         yn[i]=y[i]*aux+fty*delt2;
         zn[i]=z[i]*aux+ftz*delt2;
             }
      }
   for (i=1; i <= n; i++) {
      x[i]=xn[i];
      y[i]=yn[i];
      z[i]=zn[i];
      }
   if (itest == 1) goto Mainloop;
}

Answer 1

你问：

在C中，如何使用x从文件中读取数据

您不会在C中执行此操作。您的shell /控制台/运行时环境提供了这种功能。

如果您有一个程序x可以从stdin读取其输入，并且您有一个包含适用于y的输入的文件x，则使用：

x < y

来自shell的

。

<强>更新

我想我知道你的问题可能在哪里。你有：

char ch, file_name[25];

FILE *fp, *ofp;
//file_name=argv[0];
//char *mode = "r";

printf("Enter the name of file you wish to see\n"); //instead of this, i wanted it reads automatically, like taking data from the file and calculate it.

gets(file_name);
fp = fopen(file_name, "r");

您希望从命令行传递输入文件的名称，而不是使用gets来读取输入文件的名称。我希望我能在这方面走上正轨。

在这种情况下，您需要使用：

char* file_name = argv[1]; // argv[0] is the program name
                           // argv[1] is the first argument to the program

然后，你可以使用：

x y

其中x是您的计划，y包含x所需的输入数据。

Answer 2

这是一些非常可怕的代码。但如果您必须使用它，请尝试将main更改为：

int main()
{
  double x[m], y[m], z[m], xn[m], yn[m], zn[m];
  double delt, eps, resultant;
  int i, n, iter;

  printf("The contents of %s file are : \n", file_name);

  while (scanf("%d  %lf  %lf", &n, &delt, &eps) == 3)
    printf("n = %d, delta t = %lf and tolerance = %lf \n",n, delt, eps);

  simulate(m, n, delt, eps, x, y, z, iter, xn, yn, zn);
  printf("n = %d, delta t = %lf and tolerance = %lf \n",n, delt, eps);
  for (i=1; i <= n; i++) {
    resultant = sqrt(x[i]*x[i]+y[i]*y[i]+z[i]*z[i]);
    printf("%-5.7lf  %-5.7lf  %-5.7lf  %-5.7lf\n", x[i], y[i], z[i], resultant);
  }

  return 0;
}

在C中，如何使用x从文件中读取数据

2 个答案: