linux 如何得到设备文件的设备号（主设备号&次设备号）

使用stat (/usr/include/sys/stat.h)系统调用，接口如下：

 stat (__const char *__path, struct stat *__statbuf)

得到的信息在stat结构体中：

struct stat
  {
    __dev_t st_dev;		/* Device.  */
#if __WORDSIZE == 32
    unsigned short int __pad1;
#endif
#if __WORDSIZE == 64 || !defined __USE_FILE_OFFSET64
    __ino_t st_ino;		/* File serial number.	*/
#else
    __ino_t __st_ino;			/* 32bit file serial number.	*/
#endif
#if __WORDSIZE == 32
    __mode_t st_mode;			/* File mode.  */
    __nlink_t st_nlink;			/* Link count.  */
#else
    __nlink_t st_nlink;		/* Link count.  */
    __mode_t st_mode;		/* File mode.  */
#endif
    __uid_t st_uid;		/* User ID of the file's owner.	*/
    __gid_t st_gid;		/* Group ID of the file's group.*/
#if __WORDSIZE == 64
    int pad0;
#endif
    __dev_t st_rdev;		/* Device number, if device.  */
#if __WORDSIZE == 32
    unsigned short int __pad2;
#endif
#if __WORDSIZE == 64 || !defined __USE_FILE_OFFSET64
    __off_t st_size;			/* Size of file, in bytes.  */
#else
    __off64_t st_size;			/* Size of file, in bytes.  */
#endif
    __blksize_t st_blksize;	/* Optimal block size for I/O.  */
#if __WORDSIZE == 64 || !defined __USE_FILE_OFFSET64
    __blkcnt_t st_blocks;		/* Number 512-byte blocks allocated. */
#else
    __blkcnt64_t st_blocks;		/* Number 512-byte blocks allocated. */
#endif
#ifdef __USE_MISC
    /* Nanosecond resolution timestamps are stored in a format
       equivalent to 'struct timespec'.  This is the type used
       whenever possible but the Unix namespace rules do not allow the
       identifier 'timespec' to appear in the <sys/stat.h> header.
       Therefore we have to handle the use of this header in strictly
       standard-compliant sources special.  */
    struct timespec st_atim;		/* Time of last access.  */
    struct timespec st_mtim;		/* Time of last modification.  */
    struct timespec st_ctim;		/* Time of last status change.  */
# define st_atime st_atim.tv_sec	/* Backward compatibility.  */
# define st_mtime st_mtim.tv_sec
# define st_ctime st_ctim.tv_sec
#else
    __time_t st_atime;			/* Time of last access.  */
    unsigned long int st_atimensec;	/* Nscecs of last access.  */
    __time_t st_mtime;			/* Time of last modification.  */
    unsigned long int st_mtimensec;	/* Nsecs of last modification.  */
    __time_t st_ctime;			/* Time of last status change.  */
    unsigned long int st_ctimensec;	/* Nsecs of last status change.  */
#endif
#if __WORDSIZE == 64
    long int __unused[3];
#else
# ifndef __USE_FILE_OFFSET64
    unsigned long int __unused4;
    unsigned long int __unused5;
# else
    __ino64_t st_ino;			/* File serial number.	*/
# endif
#endif
  };

成员变量好多~

不要慌，st_rdev 就是需要设备文件对应的设备号了。

要得到主设备号&此设备号，需要使用<linux/kdev_t.h>中定义的宏：

MAJOR() 得到主设备号

MINOR() 得到次设备号

作者：ziziwu 发表于2011-10-17 19:54:29 原文链接

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