如何在C使用inotify的？ [英] How to use inotify in C?

问题描述

我搜索到的inotify相关的问题，而这一次却有所不同...

我用下面的code监视一个文件（不是目录）的变化。在测试中，当我保存的目标文件，这意味着它的工作原理则read（）不会返回。但事件 - >面膜为32768未IN_MODIFY和名称为空。另一个问题：它不能连续监测。当我更改该文件的第二次，它没有反应。感谢您的帮助！

 的#include＆LT; SYS / inotify.h＆GT;
＃包括LT＆;＆unistd.h中GT;
＃包括LT＆;＆stdio.h中GT;＃定义EVENT_SIZE（的sizeof（结构inotify_event））
的#define BUF_LEN（16 *（EVENT_SIZE + 16））诠释的main（）
{
    INT的fd;
    FD = inotify_init（）;
    如果（FD℃，）
        PERROR（inotify_init（））;    INT WD;
    WD = inotify_add_watch（FD，target.txt，IN_MODIFY）;
    如果（WD℃，）
        PERROR（inotify_add_watch）;    烧焦的buf [BUF_LEN]
    INT LEN;开始：    LEN =读（FD，BUF，BUF_LEN）;    如果（LEN大于0）
    {
        INT I = 0;
        而（I＆LT; LEN）
        {
            结构inotify_event *事件;
            事件=（结构inotify_event *）及BUF [I]            的printf（WD =％d个面具=％×饼干=％U LEN =％U \\ N，
                事件 - ＆GT; WD，事件 - ＆GT;面膜，
                事件 - ＆GT;饼干，事件 - ＆GT; LEN）;            如果（事件 - ＆GT;＆面膜放大器; IN_MODIFY）
                的printf（文件修改％S事件 - ＆GT;名）;            如果（事件 - ＆GT; LEN）
                的printf（NAME =％S \\ n，事件 - ＆GT;名）;            I + = EVENT_SIZE +事件 - ＆GT; LEN;
        }
    }    转到启动;    返回0;
}
 

解决方案

的为0x8000 对应 IN_IGNORED 。在面具的presence表示，因为该文件已被删除的inotify 手表已被删除。您大概编辑删除旧文件，并把新的文件在其位置。改变该文件，因为手表已除去第二时间没有影响。

不被返回的名称，因为你不是在看一个目录。

从 的inotify 手册页

  

的名称字段只有当返回一个事件的监控目录中的文件present;它标识相对于观看目录中的文件路径名。

  
  

...

  
  

IN_IGNORED - 手表显式删除（inotify_rm_watch（2））或自动（文件被删除或文件系统已卸载）

I searched for questions related to inotify, and this one is somewhat different...

I use the following code to monitor change of one file (not directory). In testing, the read() does return when I save the target file which means it works. But event->mask is 32768 which is not IN_MODIFY and name is empty. Another issue: it cannot monitor continuously. When I change the file the second time, it has no response. Thank you for the help!

#include <sys/inotify.h>
#include <unistd.h>
#include <stdio.h>

#define EVENT_SIZE  (sizeof (struct inotify_event))
#define BUF_LEN        (16 * (EVENT_SIZE + 16))

int main()
{
    int fd;
    fd = inotify_init();
    if (fd < 0)
        perror("inotify_init()");

    int wd;
    wd = inotify_add_watch(fd, "target.txt", IN_MODIFY);
    if (wd < 0)
        perror("inotify_add_watch");

    char buf[BUF_LEN];
    int len;

start:

    len = read(fd, buf, BUF_LEN);

    if (len > 0)
    {
        int i = 0;
        while (i < len)
        {
            struct inotify_event *event;
            event = (struct inotify_event *) &buf[i];

            printf("wd=%d mask=%x cookie=%u len=%u\n",
                event->wd, event->mask,
                event->cookie, event->len);

            if (event->mask & IN_MODIFY)
                printf("file modified %s", event->name);

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

            i += EVENT_SIZE + event->len;
        }
    }

    goto start;

    return 0;
}

解决方案

The 0x8000 corresponds to IN_IGNORED. Its presence in the mask indicates that the inotify watch had been removed because the file had been removed. Your editor probably removed the old file and put a new file in its place. Changing the file a second time had no effect because the watch had been removed.

The name is not being returned because you are not watching a directory.

From the inotify man page.

The name field is only present when an event is returned for a file inside a watched directory; it identifies the file pathname relative to the watched directory.

...

IN_IGNORED -- Watch was removed explicitly (inotify_rm_watch(2)) or automatically (file was deleted, or file system was unmounted).

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