使用fscanf读入指针时出现分段错误(内核已转储) [英] Segmentation fault (core dumped) when using fscanf to read into a pointer

问题描述

我正在尝试使用fscanf读取和打印屏幕上的每个字符，但是在运行程序时遇到了段错误(核心已转储).这是我的代码:

I'm trying to use fscanf to read and print every character on the screen, but I'm getting a segmentation fault (core dumped) when I run the program. Here's my code:

#include <stdio.h>

main(int argc, char * argv[]) {
    int *a ;
    FILE *input;

    if (argc>=2) {
        input= fopen(argv[1],"r");

        if (input!=NULL) {
            while (feof(input)==0) {
                fscanf(input,"%d\n",a);
                printf("%d\n",*a);
            }
            fclose(input);
        } else {
            printf("Error!\n");
        }
    }
}

我将文件作为参数提供，像这样:

I provide the file as an argument, like this:

./myprog input.txt

文件input.txt包含以下内容:

23
47
55
70

推荐答案

变量a未初始化为指向有效的内存地址.

Variable a is not initialized to point to a valid memory address.

因此，它很可能指向无效的内存地址.

Therefore, it is most likely pointing to an invalid memory address.

这是一种解决方法:

int *a = malloc(sizeof(int));
...
free(a); // when done using it

这是另一种解决方法:

int b;
int *a = &b;

但是我建议您按照以下步骤操作，以使其更简单，更干净...

But I suggest that you follow the steps below in order to make it simpler and cleaner...

更改此内容:

int *a;

为此:

int a;

这是

fscanf(input,"%d\n",a);

为此:

fscanf(input,"%d\n",&a);

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