c - 在 C 中通知问题

Question

我想监控对文件的修改，但它不起作用。输入示例:./es file_to_watch

这是我的代码:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <linux/limits.h>
#include <sys/inotify.h>

#define BUF_LEN sizeof(struct inotify_event) + NAME_MAX + 1 /*buffer to store the data of events*/

int main( int argc, char *argv[]){
   int fd, wd, length;
   char buffer[BUF_LEN];
   struct inotify_event *event;

   if(argc < 2){    
      exit(1);
   }
   else{
       fd = inotify_init();
       if(fd < 0){
           perror("inotify_init");
       }

       wd = inotify_add_watch(fd, argv[1], IN_OPEN | IN_MODIFY | IN_DELETE);
       if (wd == -1)
           return(1);
       else{

           while(1){
               length = read(fd, buffer, BUF_LEN); 
               if(length == -1)
                    return(0);

               event = (struct inotify_event *) &buffer;    
               if(event->len){
                    if(event->mask & IN_OPEN){
                         printf( "file %s was open.\n", event->name );
                    }
                    else if(event->mask & IN_MODIFY){
                        printf( "file %s was modify.\n", event->name );
                    }
                    else if(event->mask & IN_DELETE){
                        printf( "file %s was delete.\n", event->name );
                    break;
                    }
               }            
           }
           inotify_rm_watch(fd, wd);
           close(fd);
      }
  }
  return(0);
}

当我尝试打开文件时，没有任何反应。当我尝试更改或取消它时，同样的事情发生了。程序应该在文件被删除时结束。谢谢。

Answer 1

你有几个问题(来自 inotify man page )

1. name 字段仅在您查看目录时出现。所以在printf中使用event->name是错误的，你应该打印argv[1]。

    The name field is present only when an event is returned for a file
    inside a watched directory; it identifies the file pathname relative
    to the watched directory.  This pathname is null-terminated, and may
    include further null bytes ('\0') to align subsequent reads to a
    suitable address boundary.

1. 在您的情况下，event->mask 永远不会等于 IN_DELETE，因为

    IN_DELETE (+)
        File/directory deleted from watched directory.

  but instead

    IN_IGNORED
         Watch was removed explicitly (inotify_rm_watch(2)) or
         automatically (file was deleted, or filesystem was
         unmounted).  See also BUGS.

   when the file is deleted.

我建议您改为查看目录，并检查 event->name 以查看它是否与您提供的 argv[1] 匹配。

您还应该在read 之后有一个循环，以将所有可能的inotify_event * 读取到buffer。您可以通过指向 buffer 开头的指针并在每次迭代中将其增加 sizeof(struct inotify_event) + event->len 来实现。