Linux的bzero是什么功能

bzero是一个函数，用于将指定的内存空间中的前n个字节设置为0。它的函数原型如下：

void bzero(void *s, size_t n);

其中，s为指向欲操作的内存空间的指针，n为要设置为0的字节数。bzero函数通常用于清空内存空间，以便在使用之前可以确保其内容为空。注意，bzero已经被标记为过时函数，建议使用memset代替。

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linux ping源码

Linux的ping命令的源代码可以在网络上进行查找和下载。以下是ping命令的基本源代码：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <sys/time.h>
#include <errno.h>
#include <signal.h>

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

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
int sockfd, datalen = 56;
int nsend = 0, nreceived = 0;
struct sockaddr_in dest_addr;
pid_t pid;
struct sockaddr_in from;

void statistics(int signo);
unsigned short cal_chksum(unsigned short *addr, int len);

int main(int argc, char *argv[])
{
    struct hostent *host;
    struct timeval tv;
    struct timeval start, end;
    struct timezone tz;
    int n;
    unsigned char ttl = 64, loop = 1;
    bzero(&dest_addr, sizeof(dest_addr));

    if(argc<2)
    {
        printf("usage:%s hostname/IP address\n", argv[0]);
        exit(1);
    }

    if((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) < 0)
    {
        perror("socket");
        exit(1);
    }

    pid = getpid();

    setsockopt(sockfd, SOL_IP, IP_TTL, &ttl, sizeof(ttl));
    setsockopt(sockfd, SOL_IP, IP_MULTICAST_LOOP, &loop, sizeof(loop));

    dest_addr.sin_family = AF_INET;
    if(inet_addr(argv[1]) == INADDR_NONE)
    {
        if((host = gethostbyname(argv[1])) == NULL)
        {
            perror("gethostbyname error");
            exit(1);
        }

        memcpy((char *)&dest_addr.sin_addr, host->h_addr, host->h_length);
    }
    else
        dest_addr.sin_addr.s_addr = inet_addr(argv[1]);

    printf("PING %s (%s): %d data bytes\n", argv[1], inet_ntoa(dest_addr.sin_addr), datalen);

    tv.tv_sec = 5;
    tv.tv_usec = 0;

    setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));

    while(nsend < MAX_NO_PACKETS)
    {
        nsend++;

        gettimeofday(&start, &tz);

        memset(sendpacket, 0, sizeof(sendpacket));
        memset(recvpacket, 0, sizeof(recvpacket));

        struct icmp *icmp;
        icmp = (struct icmp*)sendpacket;
        icmp->icmp_type = ICMP_ECHO;
        icmp->icmp_code = 0;
        icmp->icmp_id = pid;
        icmp->icmp_seq = nsend;
        memset(icmp->icmp_data, '1', datalen);
        icmp->icmp_cksum = cal_chksum((unsigned short *)icmp, datalen + 8);

        if(sendto(sockfd, sendpacket, sizeof(sendpacket), 0, (struct sockaddr *)&dest_addr, sizeof(dest_addr)) < 0)
        {
            perror("sendto error");
            continue;
        }

        if(recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct sockaddr *)&from, &n) < 0)
        {
            perror("recvfrom error");
            continue;
        }

        gettimeofday(&end, &tz);

        struct ip *ip;
        struct icmp *icmp_back;
        double rtt;
        int len = 0;

        ip = (struct ip*)recvpacket;

        len = ip->ip_hl * 4;
        icmp_back = (struct icmp*)(recvpacket + len);

        if((icmp_back->icmp_type == ICMP_ECHOREPLY) && (icmp_back->icmp_id == pid))
        {
            nreceived++;

            printf("%d bytes from %s: icmp_seq=%u ttl=%d time=%.2f ms\n",
                datalen, inet_ntoa(from.sin_addr), icmp_back->icmp_seq, ip->ip_ttl, rtt);

            rtt = 1000 * (end.tv_sec - start.tv_sec) + (end.tv_usec - start.tv_usec) / 1000;
        }
        else
            printf("receive packet error!\n");

        sleep(1);
    }

    statistics(SIGALRM);

    return 0;
}

void statistics(int signo)
{
    printf("\n%d packets transmitted, %d received, %%%d lost\n", nsend, nreceived, (nsend - nreceived) / nsend * 100);
}

unsigned short cal_chksum(unsigned short *addr, int len)
{
    int nleft = len;
    int sum = 0;
    unsigned short *w = addr;
    unsigned short answer = 0;

    while(nleft > 1)
    {
        sum += *w++;
        nleft -= 2;
    }

    if(nleft == 1)
    {
        *(unsigned char *)(&answer) = *(unsigned char *)w;
        sum += answer;
    }

    sum = (sum >> 16) + (sum & 0xFFFF);
    sum += (sum >> 16);
    answer = ~sum;

    return answer;
}

这段代码实现了ping命令的基本功能，包括构建ICMP数据包、发送和接收数据包、计算RTT等。需要注意的是，此代码只作为示例，实际使用时可能需要根据具体需求进行修改和优化。