2. lstat獲取的是該符號連結本身的資訊；而stat獲取的是該連結指向的檔案的資訊；

這三個系統呼叫都依賴一個重要的結構體struct stat

struct stat {
        mode_t     st_mode;       //檔案對應的模式，檔案，目錄等
        ino_t      st_ino;        //inode節點號
        dev_t      st_dev;        //裝置號碼
        dev_t      st_rdev;       //特殊裝置號碼
        nlink_t    st_nlink;      //檔案的連線數
        uid_t      st_uid;        //檔案所有者
        gid_t      st_gid;        //檔案所有者對應的組
        off_t      st_size;       //普通檔案，對應的檔案位元組數
        time_t     st_atime;      //檔案最後被訪問的時間
        time_t     st_mtime;      //檔案內容最後被修改的時間
        time_t     st_ctime;      //檔案狀態改變時間
        blksize_t st_blksize;     //檔案內容對應的塊大小
        blkcnt_t   st_blocks;     //偉建內容對應的塊數量
      };
 

（1） 先在測試目錄下建立一個test.txt檔案，然後"ln -s test.txt link"建立一個符號檔案指向test.txt;

（2） 寫測試程式碼

#include <sys/stat.h>
#include <fcntl.h>
#include "stdio.h"
#include "time.h"
#include "unistd.h"

void report(struct stat *ptr)
{
    if(!ptr)
    {
        return;
    }
        
    printf("The device no is: %d\n", ptr->st_dev);
    printf("The file's node number is: %d\n", ptr->st_ino);
    printf("The file's access mode is: %d\n", ptr->st_mode);
    printf("The file's hard link number is: %d\n", ptr->st_nlink);
    printf("The file's user id is: %d\n", ptr->st_uid);
    printf("The file's group id is: %d\n", ptr->st_gid);
    printf("The file's size is: %d\n", ptr->st_size);
    printf("The block size is: %d\n", ptr->st_blksize);
    printf("The number of allocated blocks is: %d\n", ptr->st_blocks);

    struct tm* pAccesstime=localtime(&(ptr->st_atime));
    struct tm* pModifytime=localtime(&(ptr->st_mtime));
    struct tm* pChangetime=localtime(&(ptr->st_ctime));
    char aBuffer[64] = {0};
    char mBuffer[64] = {0};
    char cBuffer[64] = {0};
    strftime(aBuffer, 64, "The last access time is: %Y-%m-%d %H:%M:%S \n", pAccesstime);
    strftime(mBuffer, 64, "The last modify time is: %Y-%m-%d %H:%M:%S \n", pModifytime);
    strftime(cBuffer, 64, "The last change time is: %Y-%m-%d %H:%M:%S \n", pChangetime);

    printf(aBuffer);
    printf(mBuffer);
    printf(cBuffer);
}

void Test(const char* pFileName)
{
	if(!pFileName)
	{
		printf("error: file pointer is null in Test function\n");
		return;
	}
	printf("File %s is be in testing ...\n", pFileName);

	struct stat st;
	int nRev_st = stat(pFileName, &st);
	if(nRev_st < 0)
	{
		printf("File %s is not existed \n", pFileName);
	}
	else
	{
		printf("------get file %s info by stat \n", pFileName);
		report(&st);
	}

	struct stat ls;
	int nRev_ls = lstat(pFileName, &ls);
	if(nRev_ls < 0)
	{
		printf("File %s is not existed \n", pFileName);
	}
	else
	{
		printf("------get file %s info by lstat \n", pFileName);
		report(&ls);
	}

	struct stat fs;
	int fd = open(pFileName, O_RDONLY);
	int nRev_fs = fstat(fd, &fs);
	close(fd);
	if(nRev_fs < 0)
	{
		printf("File %s is not existed \n", pFileName);
	}
	else
	{
		printf("------get file %s info by fstat \n", pFileName);
		report(&fs);
	}
}

int main()
{
	const char* pFileName_Real = "test.txt";
	const char* pFileName_Link = "link";
	Test(pFileName_Real);
	printf("\n\n");
	Test(pFileName_Link);
	return 0;
}