inotify監聽文件夾的變更

inotify只能監控單層目錄變化，不能監控子目錄中的變化狀況。
若是須要監控子目錄，須要在調用inotify_add_watch(int fd, char *dir, int mask):int創建監控時，遞歸創建子目錄的監控，僞代碼以下
void addwatch(int fd, char *dir, int mask)
{
    wd = inotify_add_watch(fd, dir, mask);
    向目錄集合加入(wd, dir);
    for (dir下全部的子目錄subdir）
        addwatch(fd, subdir, mask);
}
這樣就能夠獲得一個目錄集合，其中每個wd對應一個子目錄。
當你調用read獲取信息時，能夠獲得一個下面的結構體
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，經過event->wd和剛纔記錄的目錄集合能夠知道變更的具體子目錄。
event->name爲具體的文件名稱。
event->name是一個char name[0]形式的樁指針，具體的name佔據的長度能夠由event->len得出

個人監控部分代碼以下：
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)
                                具體處理函數(event);
                        i += EVENT_SIZE + event->len;
                }
        }
        close(fd);
        exit(1);
}
在你的具體處理函數中，經過wd辨識子目錄，經過name辨識文件 

這是利用C++STLmap寫的一個範例，能夠監視當前目錄下（含子目錄）的變化，建立，刪除過程（新創建的目錄不能監視，只能經過監視到建立新目錄的事件後從新初始化監視表）
新版1.1.0，能夠監視建立的子目錄，方法是，當do_action探測到新目錄建立的動做時，調用inotify_add_watch追加新的監視
/*
    Copyright (C) 2010-2011 LIU An (SuperHacker@china.com.cn)

    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);}