inotify -- Linux 2.6 内核中的文件系统变化通知机制

https://www.ibm.com/developerworks/cn/linux/l-inotifynew/

程序实现

MonitorDir.cpp

#include <sys/unistd.h>
#include <sys/inotify.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
//_syscall0(int, inotify_init)
//_syscall3(int, inotify_add_watch, int, fd, const char *, path, __u32, mask)
//_syscall2(int, inotify_rm_watch, int, fd, __u32, mask)
char * monitored_files[] = {
	"./tmp_file",
	"./tmp_dir"
};
struct wd_name {
	int wd;
	char * name;
};
#define WD_NUM 2
struct wd_name wd_array[WD_NUM];
char * event_array[] = {
	"File was accessed",
	"File was modified",
	"File attributes were changed",
	"writtable file closed",
	"Unwrittable file closed",
	"File was opened",
	"File was moved from X",
	"File was moved to Y",
	"Subfile was created",
	"Subfile was deleted",
	"Self was deleted",
	"Self was moved",
	"",
	"Backing fs was unmounted",
	"Event queued overflowed",
	"File was ignored"
};
#define EVENT_NUM 16
#define MAX_BUF_SIZE 1024
	
int main(void)
{
	int fd;
	int wd;
	char buffer[1024];
	char * offset = NULL;
	struct inotify_event * event;
	int len, tmp_len;
	char strbuf[16];
	int i = 0;
	
	fd = inotify_init();
	if (fd < 0) {
		printf("Fail to initialize inotify.\n");
		exit(-1);
	}
	for (i=0; i<WD_NUM; i++) {
		wd_array[i].name = monitored_files[i];
		wd = inotify_add_watch(fd, wd_array[i].name, IN_ALL_EVENTS);
		if (wd < 0) {
			printf("Can't add watch for %s.\n", wd_array[i].name);
			exit(-1);
		}
		wd_array[i].wd = wd;
	}
	while(len = read(fd, buffer, MAX_BUF_SIZE)) {
		offset = buffer;
		printf("Some event happens, len = %d.\n", len);
		event = (struct inotify_event *)buffer;
		while (((char *)event - buffer) < len) {
			if (event->mask & IN_ISDIR) {
				memcpy(strbuf, "Direcotory", 11);
			}
			else {
				memcpy(strbuf, "File", 5);
			}
			printf("Object type: %s\n", strbuf);
			for (i=0; i<WD_NUM; i++) {
				if (event->wd != wd_array[i].wd) continue;
				printf("Object name: %s\n", wd_array[i].name);
				break;
			}
			printf("Event mask: %08X\n", event->mask);
			for (i=0; i<EVENT_NUM; i++) {
				if (event_array[i][0] == '\0') continue;
				if (event->mask & (1<<i)) {
					printf("Event: %s\n", event_array[i]);
				}
			}
			tmp_len = sizeof(struct inotify_event) + event->len;
			event = (struct inotify_event *)(offset + tmp_len); 
			offset += tmp_len;
		}
	}
}

编译命令

g++ MonitorDir.cpp -o Monitor

程序运行./Monitor

需要注意事项，在程序运行的目录处 建立一个tmp_file的文件  和一个tmp_dir的文件夹。此时操作两个中的任一个都会提示出现的操作。