inotify_add_watch在/ sys / class / net / eth0 / operstate上失败

我在Linux中使用了inotify，以便在网络接口链接发生变化时引发事件。 每当接口链接发生变化时，/ sys / class / net / eth40 / operstate / file都会被修改。 但是在下面的代码片段中，即使文件被修改，read函数仍然处于阻塞状态。

#include  #include  #include  #include  #include  #define FILE_TO_WATCH "/sys/class/net/eth40/operstate" #define EVENT_SIZE (sizeof (struct inotify_event)) #define EVENT_BUFFER_LENGTH (1024 * EVENT_SIZE + NAME_MAX + 1) void print_event(struct inotify_event *event) { int ret = 0; if (event->mask & IN_CREATE) printf("file created in directory\n"); if (event->mask & IN_DELETE) printf("file deleted in directory\n"); if (event->mask & IN_ACCESS) printf("file accessed\n"); if (event->mask & IN_CLOSE) printf("file closed after reading or writing \n"); if (event->mask & IN_OPEN) printf("file opened\n"); if (event->len) printf("name: %s\n", event->name); } int main(int argc, char** argv) { int notify_fd; int watch_fd; long input_len; char *ptr; char buffer[EVENT_BUFFER_LENGTH]; struct inotify_event *event; notify_fd = inotify_init(); if (notify_fd < 0) { perror("cannot init inotify"); exit(EXIT_FAILURE); } printf("done1\n"); watch_fd = inotify_add_watch(notify_fd,FILE_TO_WATCH,IN_ACCESS|IN_MODIFY); if (watch_fd < 0) { perror("cannot add file"); exit(EXIT_FAILURE); } printf("done2\n"); while (1) { input_len = read(notify_fd, buffer, EVENT_BUFFER_LENGTH); if (input_len <= 0) { perror("error reading from inotify fd"); exit(EXIT_FAILURE); } printf("done3\n"); ptr = buffer; while (ptr len; } } } 

我错过了什么？

Answer 1

/ sys不是常规文件系统，而是一个名为sysfs的特殊内存文件系统

引用内核开发人员 ：

inotify不会也不会在sysfs上运行。 或procfs。 或者是devpts。 或任意数量的网络文件系统。 无论有人希望它如何努力工作，这根本不可行。

对于网络链接事件，您可以使用rt netlink ，虽然这样的内容很难记录，这里是一个起点示例，它将向您显示链接（以及其他一些）事件，您将必须弄清楚哪些事件/标志和类似的事件与您的具体情况相关。

 #include  #include  #include  #include  #include  #include  #include  #include  #include  #define ENTRY(x) {x, #x} struct { unsigned flag; const char *name; } ifi_flag_map[] = { ENTRY(IFF_UP), ENTRY(IFF_BROADCAST), ENTRY(IFF_DEBUG), ENTRY(IFF_LOOPBACK), ENTRY(IFF_POINTOPOINT), ENTRY(IFF_NOTRAILERS), ENTRY(IFF_RUNNING), ENTRY(IFF_NOARP), ENTRY(IFF_PROMISC), ENTRY(IFF_ALLMULTI), ENTRY(IFF_MASTER), ENTRY(IFF_SLAVE), ENTRY(IFF_MULTICAST), ENTRY(IFF_PORTSEL), ENTRY(IFF_AUTOMEDIA), ENTRY(IFF_DYNAMIC), ENTRY(IFF_LOWER_UP), ENTRY(IFF_DORMANT), ENTRY(IFF_ECHO), }; struct { unsigned type; const char *name; } nlmrt_type_map[] = { ENTRY(RTM_NEWLINK ), ENTRY(RTM_DELLINK), ENTRY(RTM_GETLINK), ENTRY(RTM_SETLINK), ENTRY(RTM_NEWADDR ), ENTRY(RTM_DELADDR), ENTRY(RTM_GETADDR), ENTRY(RTM_NEWROUTE ), ENTRY(RTM_DELROUTE), ENTRY(RTM_GETROUTE), ENTRY(RTM_NEWNEIGH ), ENTRY(RTM_DELNEIGH), ENTRY(RTM_GETNEIGH), ENTRY(RTM_NEWRULE ), ENTRY(RTM_DELRULE), ENTRY(RTM_GETRULE), ENTRY(RTM_NEWQDISC ), ENTRY(RTM_DELQDISC), ENTRY(RTM_GETQDISC), ENTRY(RTM_NEWTCLASS ), ENTRY(RTM_DELTCLASS), ENTRY(RTM_GETTCLASS), ENTRY(RTM_NEWTFILTER ), ENTRY(RTM_DELTFILTER), ENTRY(RTM_NEWACTION ), ENTRY(RTM_DELACTION), ENTRY(RTM_GETACTION), ENTRY(RTM_NEWPREFIX ), ENTRY(RTM_GETMULTICAST ), ENTRY(RTM_GETANYCAST ), ENTRY(RTM_NEWNEIGHTBL ), ENTRY(RTM_GETNEIGHTBL ), ENTRY(RTM_SETNEIGHTBL), ENTRY(RTM_NEWNDUSEROPT ), ENTRY(RTM_NEWADDRLABEL ), ENTRY(RTM_DELADDRLABEL), ENTRY(RTM_GETADDRLABEL), ENTRY(RTM_GETDCB ), ENTRY(RTM_SETDCB), ENTRY(RTM_NEWNETCONF ), ENTRY(RTM_GETNETCONF ), ENTRY(RTM_NEWMDB ), ENTRY(RTM_DELMDB ), ENTRY(RTM_GETMDB ), }; void print_type(unsigned type) { size_t i; for (i = 0; i < sizeof nlmrt_type_map/sizeof nlmrt_type_map[0]; i++) { if (type == nlmrt_type_map[i].type) { printf("\t\tMsg Type: %s\n", nlmrt_type_map[i].name); return; } } printf("\t\tMsg Type: unknown(%d)\n", type); } void print_flags(unsigned flags, unsigned change) { size_t i; printf("\t\tflags: "); for (i = 0; i < sizeof ifi_flag_map/sizeof ifi_flag_map[0]; i++) { if (flags & ifi_flag_map[i].flag) { if (change & ifi_flag_map[i].flag) { printf("%s(C) ", ifi_flag_map[i].name); } else { printf("%s ", ifi_flag_map[i].name); } } } puts(""); } oid read_msg(int fd) { int len; char buf[4096]; struct iovec iov = { buf, sizeof(buf) }; struct sockaddr_nl sa; struct msghdr msg = { (void *)&sa, sizeof(sa), &iov, 1, NULL, 0, 0 }; struct nlmsghdr *nh; len = recvmsg(fd, &msg, 0); if(len == -1) { perror("recvmsg"); return; } for (nh = (struct nlmsghdr *) buf; NLMSG_OK (nh, len); nh = NLMSG_NEXT (nh, len)) { struct ifinfomsg *ifimsg; /* The end of multipart message. */ printf("netlink message: len = %u, type = %u, flags = 0x%X, seq = %u, pid = %u\n", nh->nlmsg_len, nh->nlmsg_type, nh->nlmsg_flags, nh->nlmsg_seq, nh->nlmsg_pid); if (nh->nlmsg_type == NLMSG_DONE) return; if (nh->nlmsg_type == NLMSG_ERROR) { continue; } ifimsg = NLMSG_DATA(nh); printf("\tifi_family = %u, ifi_type = %u, ifi_index = %u, ifi_flags = 0x%X, ifi_change = 0x%X\n", ifimsg->ifi_family , ifimsg->ifi_type , ifimsg->ifi_index , ifimsg->ifi_flags , ifimsg->ifi_change); print_type(nh->nlmsg_type); print_flags(ifimsg->ifi_flags, ifimsg->ifi_change); } } int main(int argc, char *argv[]) { struct sockaddr_nl sa; int fd; memset(&sa, 0, sizeof(sa)); sa.nl_family = AF_NETLINK; sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR; fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); if(fd == -1) { perror("socket"); return 1; } if(bind(fd, (struct sockaddr *) &sa, sizeof(sa)) == -1) { perror("bind"); return 1; } for(;;) { read_msg(fd); } return 0; }