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

// 讀取一個檔案的最前面n個位元組，並以十六進位制形式輸出每個位元組的值
void readNBytes(char *fileName, int n)
{
    FILE *fp = fopen(fileName, "r");
    unsigned char *buf = (unsigned char*)malloc(sizeof(unsigned char)*n);
    int i;
    
    if(fp == NULL)
    {
        printf("open file [%s] failed.\n", fileName);
        return;
    }
    
    fread(buf, sizeof(unsigned char), n, fp);
    fclose(fp);
    printf("%s:\t", fileName);
    
    for(i = 0; i < n; i++)
    {
        printf("%x\t", buf[i]);
    }
    
    printf("\n");
    free(buf);
}

void main()
{
    char fileName[][50] = {"ansi.txt", "unicode.txt", "ubigendian.txt", "utf8.txt"};
    int i;

    for(i = 0; i < 4; i++)
    {
        // 每個檔案中的內容都是：你what123456
        readNBytes(fileName[i], 3);
    }
}
 

每個測試檔案中的內容都是：你what123456

執行結果為：

ansi.txt:       c4      e3      77
unicode.txt:    ff      fe      60
ubigendian.txt: fe      ff      4f
utf8.txt:       ef      bb      bf