c - 下面的代码有什么问题？(在c中的文件管理中)

Question

#include <stdio.h>
main()
{
    FILE *f1,*f2,*f3;
    int number,i;
    printf("content of data file\n\n");
    f1 =fopen("data","w");
    for(i=0;i<20;i++)
    {
        scanf("%d",&number);
        if(number==-1)
            break;
        putw(number,f1);
    }
    fclose(f1);
    f1=fopen("data","r");
    f2=fopen("odd","w");
    f3=fopen("even","w");
    while((number=getw(f1))!=EOF)
    {
        if(number%2==0)
            putw(number,f3);
        else
        {
            putw(number,f2);
        }
        fclose(f1);
        fclose(f2);
        fclose(f3);
        f2=fopen("odd","r");
        f3=fopen("even","r");
        printf("\n\ncontent of odd file\n\n");
        while((number=getw(f2))!=EOF)
            printf("%4d",number);
        printf("\n\ncontent of even number\n\n");
        while((number=getw(f3))!=EOF)
            printf("%4d",number);
    }
}

我理解了整个程序，但是我的编译器没有给出正确的答案，我正在使用代码块。代码有什么问题，文件管理程序都无法正常工作吗？为什么？

Answer 1

你有:

while((number=getw(f1))!=EOF)
{
    if(number%2==0)
        putw(number,f3);
    else
    {
        putw(number,f2);
    }
    fclose(f1);
    fclose(f2);
    fclose(f3);

这是过早关闭文件。下次调用 getw(f1) 将出现问题 - 这是未定义的行为。

然后你就进入了同样的循环。

    f2=fopen("odd","r");
    f3=fopen("even","r");

现在f2和f3不能用来写入。

尝试:

while((number=getw(f1))!=EOF)
{
    if(number%2==0)
        putw(number,f3);
    else
    {
        putw(number,f2);
    }
}

// Now you can safely close the files.
fclose(f1);
fclose(f2);
fclose(f3);

// Reopen the files in read mode to examine their contents.
f2=fopen("odd","r");
f3=fopen("even","r");