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 <stdio.h>
#include <sys/inotify.h>
#include <stdlib.h>
#include <limits.h>
#include <signal.h>
#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 < buffer + input_len) {
event = (struct inotify_event *) ptr;
print_event(event);
ptr += sizeof (struct inotify_event) +event->len;
}
}
}
am＆＃39;我错过了什么？
答案 0 :(得分：3)
/ 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
inotify不会也不会对sysfs起作用。或procfs。或者是devpts。 或任意数量的网络文件系统。无论有多难 可能希望它起作用，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，但这里有一个起点示例，可以显示链接（以及其他一些）事件，您＆＃39 ; ll必须弄清楚哪些事件/标志以及与您的特定情况相关的类似事件。
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <asm/types.h>
#include <asm/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/if.h>
#include <linux/rtnetlink.h>
#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;
}