inotify监听文件夹的变动

inotify只能监控单层目录变化，不能监控子目录中的变化情况。
如果需要监控子目录，需要在调用inotify_add_watch(int fd, char *dir, int mask):int建立监控时，递归建立子目录的监控，伪代码如下
void addwatch(int fd, char *dir, int mask)
{
    wd = inotify_add_watch(fd, dir, mask);
    向目录集合加入(wd, dir);
    for (dir下所有的子目录subdir）
        addwatch(fd, subdir, mask);
}
这样就可以得到一个目录集合，其中每一个wd对应一个子目录。
当你调用read获取信息时，可以得到一个下面的结构体
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.  */
};
其中，通过event->wd和刚才记录的目录集合可以知道变动的具体子目录。
event->name为具体的文件名称。
event->name是一个char name[0]形式的桩指针，具体的name占据的长度可以由event->len得出

我的监控部分代码如下：
enum {EVENT_SIZE = sizeof(struct inotify_event)};
enum {BUF_SIZE = (EVENT_SIZE + 16) << 10};
void watch_mon(int fd)
{
        int i, length;
        void *buf;
        struct inotify_event *event;
        buf = malloc(BUF_SIZE);

        while ((length = read(fd, buf, BUF_SIZE)) >= 0)
        {
                i = 0;
                while (i < length)
                {
                        event = buf + i;
                        if (event->len)
                                具体处理函数(event);
                        i += EVENT_SIZE + event->len;
                }
        }
        close(fd);
        exit(1);
}
在你的具体处理函数中，通过wd辨识子目录，通过name辨识文件 

这是利用C++STLmap写的一个范例，可以监视当前目录下（含子目录）的变化，创建，删除过程（新建立的目录不能监视，只能通过监视到创建新目录的事件后重新初始化监视表）
新版1.1.0，可以监视创建的子目录，方法是，当do_action探测到新目录创建的动作时，调用inotify_add_watch追加新的监视
/*
    Copyright (C) 2010-2011 LIU An ([e-mail])

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

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

#include <unistd.h>
#include <sys/types.h>
#include <sys/inotify.h>
#include <errno.h>
#include <dirent.h>

#include <map>
#include <string>
using namespace std;

void addwatch(int, char*, int);
static int filter_action(uint32_t mask);
int watch_init(int mask, char *root);
void addwatch(int fd, char *dir, int mask);
static void do_action(int fd, struct inotify_event *event);
void watch_mon(int fd);
static void send_mess(char *name, char *act, int ewd);
void append_dir(int fd, struct inotify_event *event, int mask);

map<int, string> dirset;

enum{MASK = IN_MODIFY | IN_CREATE | IN_DELETE};

int main(int argc, char **argv)
{
        int fd;
        if (argc != 2)
        {
fprintf(stderr, "Usage: %s dir\n", argv[0]);
                exit(1);
        }

        fd = watch_init(MASK, argv[1]);
        watch_mon(fd);

        return 0;
}

int watch_init(int mask, char *root)
{
        int i, fd;

        if ((fd = inotify_init()) < 0)
perror("inotify_init");
        addwatch(fd, root, mask);
        return fd;
}

void addwatch(int fd, char *dir, int mask)
{
        int wd;
        char subdir[512];
        DIR *odir;
        struct dirent *dent;

        if ((odir = opendir(dir)) == NULL)
        {
perror("fail to open root dir");
                exit(1);
        }
        wd = inotify_add_watch(fd, dir, mask);
        dirset.insert(make_pair(wd, string(dir)));

        errno = 0;
        while ((dent = readdir(odir)) != NULL)
        {
                if (strcmp(dent->d_name, ".") == 0
                        || strcmp(dent->d_name, "..") == 0)
                        continue;
                if (dent->d_type == DT_DIR)
                {
sprintf(subdir, "%s/%s", dir, dent->d_name);
                        addwatch(fd, subdir, mask);
                }
        }

        if (errno != 0)
        {
perror("fail to read dir");
                exit(1);
        }

        closedir (odir);
}

enum {EVENT_SIZE = sizeof(struct inotify_event)};
enum {BUF_SIZE = (EVENT_SIZE + 16) << 10};

void watch_mon(int fd)
{
        int i, length;
        void *buf;
        struct inotify_event *event;
        buf = malloc(BUF_SIZE);

        while ((length = read(fd, buf, BUF_SIZE)) >= 0)
        {
                i = 0;
                while (i < length)
                {
                        event = (struct inotify_event*)(buf + i);
                        if (event->len)
                                do_action(fd, event);
                        i += EVENT_SIZE + event->len;
                }
        }
        close(fd);
        exit(1);
}

static char action[][10] =
{
        "modified",
        "accessed",
        "created",
        "removed"
};

enum{NEWDIR = IN_CREATE | IN_ISDIR};

static void do_action(int fd, struct inotify_event *event)
{
        int ia, i;

        if ((ia = filter_action(event->mask)) < 0)
                return;

        if ((event->mask & NEWDIR) == NEWDIR)
                append_dir(fd, event, MASK);

        send_mess(event->name, action[ia], event->wd);
}

void append_dir(int fd, struct inotify_event *event, int mask)
{
        char ndir[512];
        int wd;

        sprintf(ndir, "%s/%s", dirset.find(event->wd)->second.c_str(),
                        event->name);
        wd = inotify_add_watch(fd, ndir, mask);
        dirset.insert(make_pair(wd, string(ndir)));
}

static int filter_action(uint32_t mask)
{
        if (mask & IN_MODIFY)
                return 0;
        if (mask & IN_ACCESS)
                return 1;
        if (mask & IN_CREATE)
                return 2;
        if (mask & IN_DELETE)
                return 3;
        return -1;
}

static void send_mess(char *name, char *act, int ewd)
{
        char format[] = "%s was %s.\n";
        char file[512];

        sprintf(file, "%s/%s", dirset.find(ewd)->second.c_str(), name);

        printf(format, file, act);
}