C-文件操作相关例题

文件操作相关例题

1

从文件"coordinate.txt"中读取X, Y数据(共10组), 计算Z = X + Y, 并将结果写入"result.txt"中.

x y
100.671 100.888
98.793 98.853
100.717 98.931
101.630 99.191
100.489 97.056
101.035 101.438
100.727 100.325
99.697 99.245
100.294 101.370
99.213 98.288

#include <stdio.h>

int main()
{
    char header1, header2, header3 = 'z';
    float x[10], y[10], z[10];
    FILE *fp = fopen("coordinate.txt", "r");
    if(fp == NULL)
    {
        printf("ERROR");
    }
    else
    {
        fscanf(fp, "%c %c", &header1, &header2);
        for (int i = 0; i < 10; ++i)
        {
            fscanf(fp, "%f %f", &x[i], &y[i]);
            z[i] = x[i] + y[i];
        }
        fclose(fp);
    }

    FILE *fp2 = fopen("result.txt", "w");
    if(fp2 == NULL)
    {
        printf("ERROR");
    }
    else
    {
        fprintf(fp2, "%c %c %c\n", header1, header2, header3);
        for (int i = 0; i < 10; ++i)
        {
            fprintf(fp2, "%f %f %f\n", x[i], y[i], z[i]);
        }
        fclose(fp2);
    }
    return 0;
}

2

将一个主对角线上元素从1增加到5, 其余元素为0的矩阵写入到文件"matrix.txt"中.

#include <stdio.h>

int main()
{
    FILE *fp = fopen("matrix.txt", "w");
    int value = 1;
    if(fp == NULL)
        printf("ERROR");
    else
    {
        for (int i = 1; i < 6; ++i)
        {
            for (int j = 1; j < 6; ++j)
            {
                if(i == j)
                    fputc(value+48, fp);
                else
                    fputc('0', fp);
            }
            value++;
            fputc('\n', fp);
        }
        fclose(fp);
    }
    return 0;
}

3

下面是一个几何数据文件的实例 (geodata.txt), 包含线 (LINE), 矩形 (RECT) 和圆 (CIRCLE) 三种图形.

LINE         #线
0 0 10 10    #x1 y1 x2 y2
RECT         #矩形
10 10 20 20  #x1 y1 width height
CIRCLE       #圆
20 20 40     #x1 y1 r
END          #文件中无注释

• 根据不同的几何数据类型定义不同的数据结构, 存储这些数据
• 计算线的长度, 矩形和圆的面积
• 把数据和结果写入"newdata.txt"文件中

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

typedef struct
{
    int x, y;
}POINT;

typedef struct
{
    POINT p1, p2;
    float length;
}LINE;

typedef struct
{
    POINT p;
    int width, height;
    float area;
}RECT;

typedef struct
{
    POINT p;
    int r;
    float area;
}CIRCLE;

int judge(char *str)
{
    char *c1 = "LINE";
    char *c2 = "RECT";
    char *c3 = "CIRCLE";
    if(!strcmp(c1, str))
        return 1;
    if(!strcmp(c2, str))
        return 2;
    if(!strcmp(c3, str))
        return 3;
}

int main()
{
    LINE line;
    RECT rect;
    CIRCLE circle;
    char *header = NULL;
    FILE *fp = fopen("geodata.txt", "r");
    if(fp == NULL)
        printf("ERROR");
    else
    {
        fscanf(fp, "%s", header);
        while(strcmp(header, "END") != 0)
        {
            int k = judge(header);
            switch(k)
            {
                case 1:
                    fscanf(fp, "%d %d %d %d", &line.p1.x, &line.p1.y, &line.p2.x, &line.p2.y);
                    line.length = (float)sqrt((line.p1.x-line.p2.x)*(line.p1.x-line.p2.x)+(line.p1.y-line.p2.y)*(line.p1.y-line.p2.y));
                    break;
                case 2:
                    fscanf(fp, "%d %d %d %d", &rect.p.x, &rect.p.y, &rect.width, &rect.height);
                    rect.area = (float)(rect.width * rect.height);
                    break;
                case 3:
                    fscanf(fp, "%d %d %d", &circle.p.x, &circle.p.y, &circle.r);
                    circle.area = M_PI * pow(circle.r, 2);
                    break;
            }
            fscanf(fp, "%s", header);
        }
        fclose(fp);
    }

    fp = fopen("newdata.txt", "w");
    if(fp == NULL)
        printf("ERROR");
    else
    {
        fprintf(fp, "%s\n%d %d %d %d %f\n", "LINE", line.p1.x, line.p1.y, line.p2.x, line.p2.y, line.length);
        fprintf(fp, "%s\n%d %d %d %d %f\n", "RECT", rect.p.x, rect.p.y, rect.width, rect.height, rect.area);
        fprintf(fp, "%s\n%d %d %d %f\n", "CIRCLE", circle.p.x, circle.p.y, circle.r, circle.area);
        fclose(fp);
    }
    return 0;
}