使用inotify 监视文件系统变化

Linux 2.6.13 内核中新引入的文件系统变化通知机制 inotify.

使用时应该包含头文件:

 

一、inotify event & mask

    * 以下内容引用自头文件

/* Structure describing an inotify event. */
struct inotify_event
{
  int wd;          /* Watch descriptor. */
  uint32_t mask;   /* Watch mask. */
  uint32_t cookie; /* Cookie to synchronize two events. */
  uint32_t len;    /* Length (including NULs) of name. */
  char name __flexarr; /* Name. */
};

/* Supported events suitable for MASK parameter of INOTIFY_ADD_WATCH. */
#define IN_ACCESS 0x00000001 /* File was accessed. */
#define IN_MODIFY 0x00000002 /* File was modified. */
#define IN_ATTRIB 0x00000004 /* Metadata changed. */
#define IN_CLOSE_WRITE 0x00000008 /* Writtable file was closed. */
#define IN_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed. */
#define IN_CLOSE (IN_CLOSE_WRITE | IN_CLOSE_NOWRITE) /* Close. */
#define IN_OPEN 0x00000020 /* File was opened. */
#define IN_MOVED_FROM 0x00000040 /* File was moved from X. */
#define IN_MOVED_TO 0x00000080 /* File was moved to Y. */
#define IN_MOVE (IN_MOVED_FROM | IN_MOVED_TO) /* Moves. */
#define IN_CREATE 0x00000100 /* Subfile was created. */
#define IN_DELETE 0x00000200 /* Subfile was deleted. */
#define IN_DELETE_SELF 0x00000400 /* Self was deleted. */
#define IN_MOVE_SELF 0x00000800 /* Self was moved. */

/* Events sent by the kernel. */
#define IN_UNMOUNT 0x00002000 /* Backing fs was unmounted. */
#define IN_Q_OVERFLOW 0x00004000 /* Event queued overflowed. */
#define IN_IGNORED 0x00008000 /* File was ignored. */

/* Helper events. */
#define IN_CLOSE (IN_CLOSE_WRITE | IN_CLOSE_NOWRITE) /* Close. */
#define IN_MOVE (IN_MOVED_FROM | IN_MOVED_TO) /* Moves. */

/* Special flags. */
#define IN_ONLYDIR 0x01000000 /* Only watch the path if it is a
                       directory. */
#define IN_DONT_FOLLOW 0x02000000 /* Do not follow a sym link. */
#define IN_MASK_ADD 0x20000000 /* Add to the mask of an already
                       existing watch. */
#define IN_ISDIR 0x40000000 /* Event occurred against dir. */
#define IN_ONESHOT 0x80000000 /* Only send event once. */

/* All events which a program can wait on. */
#define IN_ALL_EVENTS (IN_ACCESS | IN_MODIFY | IN_ATTRIB | IN_CLOSE_WRITE \
              | IN_CLOSE_NOWRITE | IN_OPEN | IN_MOVED_FROM \
              | IN_MOVED_TO | IN_CREATE | IN_DELETE \
              | IN_DELETE_SELF | IN_MOVE_SELF)

 

二、示例代码

    int fd, wd;
    if((fd = inotify_init()) == -1) return;
    if((wd = inotify_add_watch(fd, wpath, IN_ALL_EVENTS)) == -1) return;

    unsigned char buf[sizeof(struct inotify_event) * 256];
    size_t len, i = 0;

    while(1)
    {
        i = 0;
        len = read(fd, buf, sizeof(buf));

        while(i < len)
        {
            struct inotify_event *event = (struct inotify_event*)(buf + i);

            if(event->name != NULL)
                printf("name=%s\n", event->name);

            if(event->mask & IN_CREATE)
                printf("Creat a file.\n");

            if(event->mask & IN_DELETE)
                printf("Delete a file.\n");

            if(event->mask & IN_MODIFY)
                printf("Modify a file.\n");

            i += sizeof(struct inotify_event) + event->len;
        }
    }