Question

我无法从文件中读取单个数据点。它应该能够读取两列数据（例如x和y值），但我发现我的代码甚至无法读取单个双精度值。任何帮助，将不胜感激。

该文件位于D:\test.txt 并且只有1.11111的单个值。

输入翼型坐标的文件（文本文件）的位置：D：\ test.txt 有1行 x和y中的数据量是1点和1点。没读过。 *流程返回1 * 按任意键继续......

这是我的意见。

/*
    Purpose:
        Create a program that can take in a list of data points that represents an airfoil from some file.
        Then through the use of spline function, spline the data points for interpolation then go on to plotting them.
        With these data points, use the Vortex Panel Method to obtain coefficients of lift, pressure, and tangential velocity.
        Then after these are calculated, plot each with respect to the splined x data points.
*/

#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
#include <stdlib.h>
#define LEN 12

int countlines(FILE *fp);

int main (void)
{
    char airfoil[500];
    double *x_data = NULL; 
    double *y_data = NULL;
    FILE *pfile = NULL;
    int line_count = 0;
    double test = 0.0;


    printf("Enter the location of file (text file) of the airfoil coordinates: ");
    scanf("%s", airfoil);

    if(fopen_s(&pfile, airfoil, "r"))
    {
        printf("Error opening the file for reading the data. Program terminated.\n");
        exit(1);
    }

    line_count = countlines(pfile);

    printf("There are %d lines\n", line_count);

    x_data = realloc(x_data, line_count*(sizeof(double)));
    y_data = realloc(y_data, line_count*(sizeof(double)));

    if((!x_data) || (!y_data))
    {
        printf("Memory allocation has failed. Exiting...\n");
        exit(1);
    }

    printf("The amount of data in x and y is %zu points and %zu points.\n", (sizeof(x_data)/sizeof(double)), (sizeof(y_data)/sizeof(double)));

     if(EOF == fscanf_s(pfile, "%lf", &test))
     {
            printf("failed to read.\n");
            exit(1);
    } 
    //for(int i = 0; i < line_count; i++)
    //{
        //fscanf(pfile, " %lf", &x_data[i]);
    //}

    printf("The x-data are %lf!\n", test);
    //for(int i = 0; i < line_count; i++)
    //{
        //printf("%.2lf", x_data[i]);
        //printf("\n");
    //}

    return 0;
}

int countlines(FILE *fp)
{   
    int lines = 0;
    char str[LEN];
    while(!feof(fp))
    {  
        if (fgets(str, LEN, fp) != NULL);
            {
                lines++;
            }
    }

    return lines;
}

Answer 1

countlines只是将文件指针带到文件末尾。在您阅读任何内容之前，您必须先将文件倒回到开头：

fseek(pfile,0,SEEK_SET);

你可以在countlines()中完成。

另见评论，发现更多错误。

无法从文件中读取单个double值（C）

1 个答案: