为什么我的简单的C程序显示垃圾到标准输出？ [英] Why is my simple C program displaying garbage to stdout?

问题描述

考虑一个文件读入缓冲区，并显示该缓冲区到控制台下面简单的C程序：

Consider the following simple C program that read a file into a buffer and displays that buffer to the console:

#include<stdio.h>

main()
{
  FILE *file;
    char *buffer;
    unsigned long fileLen;
    //Open file
    file = fopen("HelloWorld.txt", "rb");
    if (!file)
    {
        fprintf(stderr, "Unable to open file %s", "HelloWorld.txt");
        return;
    }
    //Get file length
    fseek(file, 0, SEEK_END);
    fileLen=ftell(file);
    fseek(file, 0, SEEK_SET);
    //Allocate memory
    buffer=(char *)malloc(fileLen+1);
    if (!buffer)
    {
        fprintf(stderr, "Memory error!");
        fclose(file);
        return;
    }
    //Read file contents into buffer
    fread(buffer, fileLen, 1, file);
    //Send buffer contents to stdout
    printf("%s\n",buffer);    
    fclose(file);
}

它只会读取的文件包括：

The file it will read simply contains:

世界，你好！

输出是：

世界，你好！²²²²▌▌▌▌▌▌▌↔☺

Hello World!²²²²▌▌▌▌▌▌▌↔☺

这已经有一段时间，因为我做了什么在C / C ++显著，但通常我会假设正在分配的缓冲区大于必需的，但是这似乎并不如此。

It has been a while since I did anything significant in C/C++, but normally I would assume the buffer was being allocated larger than necessary, but this does not appear to be the case.

fileLen结束是12，这是正确的。

fileLen ends up being 12, which is accurate.

我现在想，我一定只是显示缓冲区错了，但我不知道我做错了。

I am thinking now that I must just be displaying the buffer wrong, but I am not sure what I am doing wrong.

任何人都可以给我介绍一下我做错了？

Can anyone clue me in to what I am doing wrong?

推荐答案

您需要NUL，终止字符串。添加

You need to NUL-terminate your string. Add

buffer[fileLen] = 0;

在打印。

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