设备特殊文件

struct stat 
{	
    mode_t             st_mode;	        /* file type & mode (permissions) */	
    ino_t	           st_ino;	        /* i-node number (serial number) */
    dev_t	           st_dev;	        /* device number (file system) */
    dev_t	           st_rdev;	        /* device number for special files */
    nlink_t	           st_nlink;	    /* number of links */
    uid_t	           st_uid;	        /* user ID of owner */
    gid_t	           st_gid;	        /* group ID of owner */
    off_t	           st_size;	        /* size in bytes, for regular files */
    struct timespec	   st_atim;	        /* time of last access */
    struct timespec	   st_mtim;	        /* time of last modification */
    struct timespec	   st_ctim;	        /* time of last file status change */
    blksize_t	       st_blksize;	    /* best I/O block size */
    blkcnt_t	       st_blocks;	    /* number of disk blocks allocated */
};	

typedef __dev_t dev_t;

#define major(dev) gnu_dev_major (dev)

/**
 * 为每个命令行参数打印设备号，另外，若此参数引用的是字符特殊文件或者块特殊文件，
 * 则还打印特殊文件的st_rdev值
 */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
    struct stat buf;
    int i = 0;
    for (i = 1; i < argc; i++)
    {
        printf("%s: ", argv[i]);
        if (stat(argv[i], &buf) < 0)
        {
            err_ret("stat error");
            continue;
        }
        printf("dev = %d/%d ", major(buf.st_dev), minor(buf.st_dev));
        if (S_ISCHR(buf.st_mode))
        {
            printf("(character) rdev = %d/%d", major(buf.st_rdev), minor(buf.st_rdev));
        }
        else if (S_ISBLK(buf.st_mode))
        {
            printf("(block) rdev = %d/%d", major(buf.st_rdev), minor(buf.st_rdev));
        }
        printf("\n");
    }
    exit(0);
}