用c写一个一直 ping 一个ip地址 如果ping不到就给ret值为1

以下是一个简单的 C 语言程序，可以一直 ping 一个 IP 地址，如果 ping 不通则返回 1：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/ip_icmp.h>
#include <netdb.h>

#define PACKET_SIZE 4096
#define MAX_WAIT_TIME 5
#define MAX_NO_PACKETS 3

struct packet
{
    struct icmphdr hdr;
    char msg[PACKET_SIZE-sizeof(struct icmphdr)];
};

unsigned short checksum(void *b, int len)
{
    unsigned short *buf = (unsigned short *)b;
    unsigned int sum = 0;
    unsigned short result;

    for (sum = 0; len > 1; len -= 2)
        sum += *buf++;

    if (len == 1)
        sum += *(unsigned char*)buf;

    sum = (sum >> 16) + (sum & 0xFFFF);
    sum += (sum >> 16);
    result = ~sum;
    return result;
}

int ping(char *host)
{
    struct hostent *hname;
    struct sockaddr_in addr_ping;
    int sockfd, i, len, flag = 1, flag_recv = 1;
    struct packet pkt;
    struct timeval tv_begin, tv_end, tv_interval;
    float rtt = 0;

    memset(&addr_ping, 0, sizeof(addr_ping));
    addr_ping.sin_family = AF_INET;

    if ((hname = gethostbyname(host)) == NULL)
    {
        printf("Unknown host %s\n", host);
        return 1;
    }

    memcpy(&addr_ping.sin_addr, hname->h_addr, sizeof(addr_ping.sin_addr));
    printf("PING %s (%s): %d bytes data in ICMP packets.\n", hname->h_name, inet_ntoa(addr_ping.sin_addr), (int)sizeof(struct packet));

    if ((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) < 0)
    {
        printf("socket error\n");
        return 1;
    }

    while (flag)
    {
        flag_recv = 1;
        memset(&pkt, 0, sizeof(pkt));
        pkt.hdr.type = ICMP_ECHO;
        pkt.hdr.code = 0;
        pkt.hdr.checksum = checksum(&pkt, sizeof(pkt));

        if (sendto(sockfd, &pkt, sizeof(pkt), 0, (struct sockaddr *)&addr_ping, sizeof(addr_ping)) < 0)
        {
            printf("sendto error\n");
            continue;
        }

        gettimeofday(&tv_begin, NULL);

        len = sizeof(addr_ping);

        if (recvfrom(sockfd, &pkt, sizeof(pkt), 0, (struct sockaddr *)&addr_ping, (socklen_t *)&len) < 0)
        {
            printf("recvfrom error\n");
            flag_recv = 0;
        }
        else
        {
            gettimeofday(&tv_end, NULL);

            tv_interval.tv_sec = tv_end.tv_sec - tv_begin.tv_sec;
            tv_interval.tv_usec = tv_end.tv_usec - tv_begin.tv_usec;

            rtt = tv_interval.tv_sec * 1000.0 + tv_interval.tv_usec / 1000.0;
            printf("%d bytes from %s: icmp_seq=%u ttl=%d time=%.1f ms\n", sizeof(pkt), inet_ntoa(addr_ping.sin_addr), pkt.hdr.un.echo.sequence, pkt.hdr.un.echo.sequence, rtt);
            flag_recv = 1;
        }

        sleep(1);

        if (!flag_recv)
        {
            flag = 0;
            printf("ping %s fail\n", host);
            close(sockfd);
            return 1;
        }

        if (i >= MAX_NO_PACKETS)
        {
            flag = 0;
        }
    }

    close(sockfd);
    return 0;
}

int main(int argc, char *argv[])
{
    if (argc < 2)
    {
        printf("Usage: %s <hostname>\n", argv[0]);
        return 1;
    }

    return ping(argv[1]);
}

注意：该程序需要在 Linux 环境下运行，并且需要 root 权限才能发送 ICMP 包。