Linux/Unix系统编程手册-笔记18.监控文件事件

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#include <sys/inotify.h>
#include <limits.h>
#include "tlpi_hdr.h"
static void /* 这一坨函数只是打印出变化事件 */

displayInotifyEvent(struct inotify_event *i)
{
    printf(" wd =%2d; ", i->wd);
    if (i->cookie > 0)
    printf("cookie =%4d; ", i->cookie);
    printf("mask = ");
    if (i->mask & IN_ACCESS) printf("IN_ACCESS ");
    if (i->mask & IN_ATTRIB) printf("IN_ATTRIB ");
    if (i->mask & IN_CLOSE_NOWRITE) printf("IN_CLOSE_NOWRITE ");
    if (i->mask & IN_CLOSE_WRITE) printf("IN_CLOSE_WRITE ");
    if (i->mask & IN_CREATE) printf("IN_CREATE ");
    if (i->mask & IN_DELETE) printf("IN_DELETE ");
    if (i->mask & IN_DELETE_SELF) printf("IN_DELETE_SELF ");
    if (i->mask & IN_IGNORED) printf("IN_IGNORED ");
    if (i->mask & IN_ISDIR) printf("IN_ISDIR ");
    if (i->mask & IN_MODIFY) printf("IN_MODIFY ");
    if (i->mask & IN_MOVE_SELF) printf("IN_MOVE_SELF ");
    if (i->mask & IN_MOVED_FROM) printf("IN_MOVED_FROM ");
    if (i->mask & IN_MOVED_TO) printf("IN_MOVED_TO ");
    if (i->mask & IN_OPEN) printf("IN_OPEN ");
    if (i->mask & IN_Q_OVERFLOW) printf("IN_Q_OVERFLOW ");
    if (i->mask & IN_UNMOUNT) printf("IN_UNMOUNT ");
    printf("\n");
    if (i->len > 0)
    printf(" name = %s\n", i->name);
}
#define BUF_LEN (10 * (sizeof(struct inotify_event) + NAME_MAX + 1))


/*下面是使用inotify的三个步骤*/

int
main(int argc, char *argv[])
{
    int inotifyFd, wd, j;
    char buf[BUF_LEN];
    ssize_t numRead;
    char *p;
    struct inotify_event *event;
    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s pathname... \n", argv[0]);

    /*
        step 1: 调用inotify_init()创建一个inotify实例
    */
    inotifyFd = inotify_init(); /* Create inotify instance */
    if (inotifyFd == -1)
        errExit("inotify_init");

    for (j = 1; j < argc; j++) {
        /*
            step 2 : int inotify_add_watch(int fd, const char *pathname, uint32_t mask);
            添加想要监控的目录路径，mask可以指定监控哪些事件，这里监控所有事件
        */
        wd = inotify_add_watch(inotifyFd, argv[j], IN_ALL_EVENTS);
        if (wd == -1)
        errExit("inotify_add_watch");
        printf("Watching %s using wd %d\n", argv[j], wd);
    }

    for (;;) { /* Read events forever */
        /*
            step 3 : 读取事件，若没有事件会阻塞
        */
        numRead = read(inotifyFd, buf, BUF_LEN);
        if (numRead == 0)
        fatal("read() from inotify fd returned 0!");
        if (numRead == -1)
        errExit("read");
        printf("Read %ld bytes from inotify fd\n", (long) numRead);
        /* Process all of the events in buffer returned by read() */
        for (p = buf; p < buf + numRead; ) {
            event = (struct inotify_event *) p;
            displayInotifyEvent(event);
            p += sizeof(struct inotify_event) + event->len;
        }
    }
    exit(EXIT_SUCCESS);
}

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struct inotify_event {
    int wd; /* Watch descriptor on which event occurred */
    uint32_t mask; /* Bits describing event that occurred */
    uint32_t cookie; /* Cookie for related events (for rename()) */
    uint32_t len; /* Size of 'name' field */
    char name[]; /* Optional null-terminated filename */
};