在C问题中将字符串转换为float？

So I have a C program where you type a name, age and height as command line prompts and these arguments are written to a text file, however, with the height (which is a float), there's a problem. It writes down a value that is really high and isn't what you type in. I feel like there's a problem with the memory or something similar.

所以我有一个C程序，你输入一个名称，年龄和高度作为命令行提示，这些参数写入文本文件，但是，高度（这是一个浮点数），有一个问题。它写下了一个非常高的值，而不是你输入的内容。我觉得内存或类似内容存在问题。

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

int main(int argc, char *argv[]) {
    if (argc != 4) {
        printf("Please enter four parameters");
        return;
    } else {
        char name[20];
        strcpy(name, argv[1]);
        int age = atoi(argv[2]);
        double height = atof(argv[3]);
        FILE *fp;

        fp = fopen("name.txt", "w+");
        fprintf(fp, "%s\n%d\n%.2f", name, age, height);
        fclose(fp);

        printf("File written!");

        return 0;
    }
}

So what have I done wrong with the float height?

那么浮标高度我做错了什么？

1 个解决方案

#1

You have to include proper header (stdlib.h) or declare the functions before using them to use atoi() and atof().

您必须包含正确的标头（stdlib.h）或在使用它们之前声明函数以使用atoi（）和atof（）。

Also note that

另请注意

using return; (return statement without return value) isn't good in non-void function.
使用回报; （没有返回值的return语句）在非void函数中不好。
you should check whether fopen() was successful.
你应该检查fopen（）是否成功。

Try this:

尝试这个：

#include <stdio.h>
#include <stdlib.h> /* add this */
#include <string.h>

int main(int argc, char *argv[]) {
    if(argc != 4) {
        printf("Please enter four parameters");
        return 1; /* add a return value */
    }
    else {
        char name[20];
        strcpy(name, argv[1]);
        int age = atoi(argv[2]);
        double height = atof(argv[3]);
        FILE *fp;

        fp = fopen("name.txt", "w+");
        if(fp == NULL) { /* add error check */
            perror("fopen");
            return 1;
        }
        fprintf(fp, "%s\n%d\n%.2f", name, age, height);
        fclose(fp);

        printf("File written!");

        return 0;
    }
}

#1