关于C语言执行CMD命令的问题

Posted 2023-05-07

问几个新手问题,C语言中可以用system("命令")来执行CMD命令
问题1:用scanf("%c",&a)输入一个盘符后.怎么用system()来进入盘符,为什么不能用system("%c:",a)来进入

问题2:当命令中出现"\"这个符号时,C就会检测到错误.比如system("md undel..\")这个设置当前文件夹为不可删除的命令不能执行.system("md undel..")就可以,但是实现的只是在当前目录建立一个名为undel的文件夹.
这个请问怎么解决.
第二个问题有点错了.不是设置当前文件夹为不可删除,只是建立一个名位undel.的不可删除文件夹.可是不加"\"就能删了.所以想问怎么在system()里面用"\".

1.
char buff[10];
fprintf(buff,"%c:",a);
system(buff);
不能用system("%c:",a)是因为system接受字符串参数后并不把它当做格式化字符串。而scanf和fprintf是将第一个参数解释为格式化字符串的（并不是C的功能，而是在自己实现的。不过既然是标准库，将其看为C的一部分也可以）。

2.
system("md undel..\\");
就可以了。
双引号里的“\\”和上面的格式化字符串不一样，它是C的一部分。这个替换是在编译时完成的（上例是运行时完成）。"\\"通过这个语法，可以在字符串中插入“\”符号。 参考技术A 问题1，要用绝对路径，否则就认为是在当前目录中的。

问题2，单独的\会和后面的字符一起被系统理解为是转义字符，不会解释为斜线，要用斜线，就写成\\ 参考技术B md只对它的工作路径起作用。
改变它的工作路径。

C语言与网络问题 高手进

用C程序实现PING命令 给出注释和流程图

参考技术A ping命令是dos命令可以创建一个cmd进程,然后建立两个管道用来得到结果 实现.

下面是一个网络编程的实例, Syn扫描器代码,可以作为参考.
基本可以看为是 ping命令的实现
//getallIP.cpp
#include <winsock2.h>
#include <stdio.h>
#pragma comment(lib,"ws2_32.lib")
int main()

////////////////
// 初始化 Windows sockets API.
//
WORD wVersionRequested = MAKEWORD(2, 2);
WSADATA wsaData;
if (WSAStartup(wVersionRequested, &wsaData))
printf("WSAStartup failed %s\n", WSAGetLastError());
return 0;


//////////////////
// 获得主机名.
//
char hostname[256];
int res = gethostname(hostname, sizeof(hostname));
if (res != 0)
printf("Error: %u\n", WSAGetLastError());
return 0;

printf("hostname=%s\n", hostname);
////////////////
// 根据主机名获取主机信息.
//
hostent* pHostent = gethostbyname(hostname);
if (pHostent==NULL)
printf("Error: %u\n", WSAGetLastError());
return 0;

//////////////////
// 解析返回的hostent信息.
//
hostent& he = *pHostent;
printf("name=%s\naliases=%s\naddrtype=%d\nlength=%d\n",
he.h_name, he.h_aliases, he.h_addrtype, he.h_length);

sockaddr_in sa;
//根据 he.h_addr_list[nAdapter]是否为空来获取所有IP地址
for (int nAdapter=0; he.h_addr_list[nAdapter]; nAdapter++)
memcpy ( &sa.sin_addr.s_addr, he.h_addr_list[nAdapter],he.h_length);
// 输出机器的IP地址.
printf("Address [%d%]: %s\n",nAdapter, inet_ntoa(sa.sin_addr)); // 显示地址串

//////////////////
// 终止 Windows sockets API
//
WSACleanup();
return 0;

//mstcpip.h
// Copyright (C) Microsoft Corporation, 1996-1999
#if _MSC_VER > 1000
#pragma once
#endif
/* Argument structure for SIO_KEEPALIVE_VALS */

struct tcp_keepalive
u_long onoff;
u_long keepalivetime;
u_long keepaliveinterval;
;

// New WSAIoctl Options

#define SIO_RCVALL _WSAIOW(IOC_VENDOR,1)
#define SIO_RCVALL_MCAST _WSAIOW(IOC_VENDOR,2)
#define SIO_RCVALL_IGMPMCAST _WSAIOW(IOC_VENDOR,3)
#define SIO_KEEPALIVE_VALS _WSAIOW(IOC_VENDOR,4)
#define SIO_ABSORB_RTRALERT _WSAIOW(IOC_VENDOR,5)
#define SIO_UCAST_IF _WSAIOW(IOC_VENDOR,6)
#define SIO_LIMIT_BROADCASTS _WSAIOW(IOC_VENDOR,7)
#define SIO_INDEX_BIND _WSAIOW(IOC_VENDOR,8)
#define SIO_INDEX_MCASTIF _WSAIOW(IOC_VENDOR,9)
#define SIO_INDEX_ADD_MCAST _WSAIOW(IOC_VENDOR,10)
#define SIO_INDEX_DEL_MCAST _WSAIOW(IOC_VENDOR,11)
//synscan.cpp
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>

#include <time.h>
#include "mstcpip.h"
#pragma comment(lib,"ws2_32.lib")
#define SEQ 0x28376839

SOCKET sockRaw = INVALID_SOCKET,
sockListen = INVALID_SOCKET;
struct sockaddr_in dest;

BOOL ScanOK=FALSE;
char *DEST_HOST;
int DEST_PORT;
int DEST_PORTEND;
int play=0;
clock_t start,end;//程序运行的起始和结束时间
float costtime;//程序耗时

typedef struct _iphdr

unsigned char h_lenver; //4位首部长度+4位IP版本号
unsigned char tos; //8位服务类型TOS
unsigned short total_len; //16位总长度（字节）
unsigned short ident; //16位标识
unsigned short frag_and_flags; //3位标志位
unsigned char ttl; //8位生存时间 TTL
unsigned char proto; //8位协议 (TCP, UDP 或其他)
unsigned short checksum; //16位IP首部校验和
unsigned int sourceIP; //32位源IP地址
unsigned int destIP; //32位目的IP地址
IP_HEADER;

typedef struct _tcphdr //定义TCP首部

USHORT th_sport; //16位源端口
USHORT th_dport; //16位目的端口
unsigned int th_seq; //32位序列号
unsigned int th_ack; //32位确认号
unsigned char th_lenres; //4位首部长度/6位保留字
unsigned char th_flag; //6位标志位
USHORT th_win; //16位窗口大小
USHORT th_sum; //16位校验和
USHORT th_urp; //16位紧急数据偏移量
TCP_HEADER;

struct //定义TCP伪首部

unsigned long saddr; //源地址
unsigned long daddr; //目的地址
char mbz;
char ptcl; //协议类型
unsigned short tcpl; //TCP长度
psd_header;

//SOCK错误处理程序
void CheckSockError(int iErrorCode, char *pErrorMsg)

if(iErrorCode==SOCKET_ERROR)

printf("%s Error:%d\n", pErrorMsg, GetLastError());
closesocket(sockRaw);
ExitProcess(-1);




//计算检验和
USHORT checksum(USHORT *buffer, int size)

unsigned long cksum=0;
while (size > 1)

cksum += *buffer++;
size -= sizeof(USHORT);

if (size)

cksum += *(UCHAR*)buffer;

cksum = (cksum >> 16) + (cksum & 0xffff);
cksum += (cksum >>16);
return (USHORT)(~cksum);


//IP解包程序
bool DecodeIPHeader(char *buf, int bytes)

IP_HEADER *iphdr;
TCP_HEADER *tcphdr;
unsigned short iphdrlen;
iphdr = (IP_HEADER *)buf;
iphdrlen = sizeof(unsigned long) * (iphdr->h_lenver & 0xf);
tcphdr = (TCP_HEADER*)(buf + iphdrlen);
//是否来自目标IP
if(iphdr->sourceIP != dest.sin_addr.s_addr) return false;

//序列号是否正确
if((ntohl(tcphdr->th_ack) != (SEQ+1)) && (ntohl(tcphdr->th_ack) != SEQ)) return false;
//if(tcphdr->th_flag == 20)return true;
//SYN/ACK - 扫描到一个端口
if(tcphdr ->th_flag == 18)

printf("\t%d\t open \n",ntohs(tcphdr->th_sport));
return true;


return true;


void usage(void)

printf("\t===================SYN portscaner======================\n");
printf("\t============[e-mail] 2004/7/6===========\n");
printf("\tusage: synscan DomainName[IP] StartPort-EndPort\n");
printf("\tExample: synscan www.163.com 1-139\n");
printf("\tExample: synscan 192.168.1.1 8000-9000\n");


DWORD WINAPI RecvThread(LPVOID para)//接收数据线程函数

int iErrorCode;
struct hostent *hp;
char RecvBuf[65535]=0;
sockListen = socket(AF_INET , SOCK_RAW , IPPROTO_IP);
CheckSockError(sockListen, "socket");

//设置IP头操作选项
BOOL bOpt = true;
iErrorCode = setsockopt(sockRaw,IPPROTO_IP,IP_HDRINCL,(char *)&bOpt,sizeof(bOpt));
CheckSockError(iErrorCode, "setsockopt()");

//获得本地IP
SOCKADDR_IN sa;
unsigned char LocalName[256];

iErrorCode = gethostname((char*)LocalName,sizeof(LocalName)-1);
CheckSockError(iErrorCode, "gethostname()");
if((hp = gethostbyname((char*)LocalName)) == NULL)

CheckSockError(SOCKET_ERROR, "gethostbyname()");

memcpy(&sa.sin_addr.S_un.S_addr,hp->h_addr_list[1],hp->h_length);
sa.sin_family = AF_INET;
sa.sin_port = htons(7000);
iErrorCode = bind(sockListen, (PSOCKADDR)&sa, sizeof(sa));
CheckSockError(iErrorCode, "bind");

//设置SOCK_RAW为SIO_RCVALL，以便接收所有的IP包
DWORD dwBufferLen[10] ;
DWORD dwBufferInLen = 1 ;
DWORD dwBytesReturned = 0 ;
iErrorCode=WSAIoctl(sockListen, SIO_RCVALL,&dwBufferInLen, sizeof

(dwBufferInLen),&dwBufferLen, sizeof(dwBufferLen),&dwBytesReturned , NULL , NULL );
CheckSockError(iErrorCode, "Ioctl");
memset(RecvBuf, 0, sizeof(RecvBuf));
//接收数据
for(;;)


iErrorCode = recv(sockListen, RecvBuf, sizeof(RecvBuf), 0);
//CheckSockError(iErrorCode, "recv");
DecodeIPHeader(RecvBuf,iErrorCode) ;

if(ScanOK)

closesocket(sockListen);
return 0;



void playx(void) // 定义状态提示函数

// 进度条
char *plays[12]=

" | ",
" / ",
" - ",
" \\ ",
" | ",
" / ",
" - ",
" \\ ",
" | ",
" / ",
" - ",
" \\ ",
;
printf(" =%s=\r", plays[play]);
play=(play==11)?0:play+1;
Sleep(2);


//主函数
int main(int argc,char **argv)

char *p;
if(argc!=3)

usage();
return 0;


p=argv[2];//处理端口参数
if(strstr(argv[2],"-"))
DEST_PORT=atoi(argv[2]);
for(;*p;)
if(*(p++)=='-')break;
DEST_PORTEND=atoi(p);

if(DEST_PORT<1 || DEST_PORTEND>65535)
printf("Port Error!\n");
return 0;




DEST_HOST=argv[1];

usage();

int iErrorCode;
int datasize;
struct hostent *hp;
IP_HEADER ip_header;
TCP_HEADER tcp_header;
char SendBuf[128]=0;

//初始化SOCKET
WSADATA wsaData;
iErrorCode = WSAStartup(MAKEWORD(2,2),&wsaData);
CheckSockError(iErrorCode, "WSAStartup()");
sockRaw = socket(AF_INET , SOCK_RAW , IPPROTO_IP);
CheckSockError(sockRaw, "socket()");
sockListen = socket(AF_INET , SOCK_RAW , IPPROTO_IP);
CheckSockError(sockListen, "socket");

//设置IP头操作选项
BOOL bOpt = true;
iErrorCode = setsockopt(sockRaw,IPPROTO_IP,IP_HDRINCL,(char *)&bOpt,sizeof(bOpt));
CheckSockError(iErrorCode, "setsockopt()");

//获得本地IP
SOCKADDR_IN sa;
unsigned char LocalName[256];

iErrorCode = gethostname((char*)LocalName,sizeof(LocalName)-1);
CheckSockError(iErrorCode, "gethostname()");
if((hp = gethostbyname((char*)LocalName)) == NULL)

CheckSockError(SOCKET_ERROR, "gethostbyname()");


memcpy(&sa.sin_addr.S_un.S_addr,hp->h_addr_list[1],hp->h_length);
sa.sin_family = AF_INET;
sa.sin_port = htons(7000);
iErrorCode = bind(sockListen, (PSOCKADDR)&sa, sizeof(sa));
CheckSockError(iErrorCode, "bind");

//获得目标主机IP
memset(&dest,0,sizeof(dest));
dest.sin_family = AF_INET;
dest.sin_port = htons(DEST_PORT);
if((dest.sin_addr.s_addr = inet_addr(DEST_HOST)) == INADDR_NONE)

if((hp = gethostbyname(DEST_HOST)) != NULL)

memcpy(&(dest.sin_addr),hp->h_addr_list[1],hp->h_length);
dest.sin_family = hp->h_addrtype;
printf("dest.sin_addr = %s\n",inet_ntoa(dest.sin_addr));

else

CheckSockError(SOCKET_ERROR, "gethostbyname()");



//开启监听线程
HANDLE Thread=CreateThread(NULL,0,RecvThread,0,0,0);

//填充IP首部
ip_header.h_lenver=(4<<4 | sizeof(ip_header)/sizeof(unsigned long));
//高四位IP版本号，低四位首部长度
ip_header.total_len=htons(sizeof(IP_HEADER)+sizeof(TCP_HEADER)); //16位总长度（字节）
ip_header.ident=1; //16位标识
ip_header.frag_and_flags=0; //3位标志位
ip_header.ttl=128; //8位生存时间TTL
ip_header.proto=IPPROTO_TCP; //8位协议(TCP,UDP…)
ip_header.checksum=0; //16位IP首部校验和
ip_header.sourceIP=sa.sin_addr.s_addr; //32位源IP地址
ip_header.destIP=dest.sin_addr.s_addr; //32位目的IP地址

//填充TCP首部
tcp_header.th_sport=htons(7000); //源端口号
tcp_header.th_lenres=(sizeof(TCP_HEADER)/4<<4|0); //TCP长度和保留位
tcp_header.th_win=htons(16384);

//填充TCP伪首部（用于计算校验和，并不真正发送）
psd_header.saddr=ip_header.sourceIP;
psd_header.daddr=ip_header.destIP;
psd_header.mbz=0;
psd_header.ptcl=IPPROTO_TCP;
psd_header.tcpl=htons(sizeof(tcp_header));

Sleep(500);
printf("\n");
printf("Scaning %s\n",DEST_HOST);
start=clock();//开始计时

for(;DEST_PORT<DEST_PORTEND;DEST_PORT++)


playx();
tcp_header.th_dport=htons(DEST_PORT); //目的端口号
tcp_header.th_ack=0; //ACK序列号置为0
tcp_header.th_flag=2; //SYN 标志
tcp_header.th_seq=htonl(SEQ); //SYN序列号
tcp_header.th_urp=0; //偏移
tcp_header.th_sum=0; //校验和
//计算TCP校验和，计算校验和时需要包括TCP pseudo header
memcpy(SendBuf,&psd_header,sizeof(psd_header));
memcpy(SendBuf+sizeof(psd_header),&tcp_header,sizeof(tcp_header));
tcp_header.th_sum=checksum((USHORT *)SendBuf,sizeof(psd_header)+sizeof(tcp_header));

//计算IP校验和
memcpy(SendBuf,&ip_header,sizeof(ip_header));
memcpy(SendBuf+sizeof(ip_header),&tcp_header,sizeof(tcp_header));
memset(SendBuf+sizeof(ip_header)+sizeof(tcp_header),0,4);
datasize=sizeof(ip_header)+sizeof(tcp_header);
ip_header.checksum=checksum((USHORT *)SendBuf,datasize);

//填充发送缓冲区
memcpy(SendBuf,&ip_header,sizeof(ip_header));

//发送TCP报文
iErrorCode=sendto(sockRaw,SendBuf,datasize,0,(struct sockaddr*) &dest,
sizeof(dest));
CheckSockError(iErrorCode, "sendto()");

end=clock();//计时结束
ScanOK=TRUE;
printf("Closeing Thread.....\n");
WaitForSingleObject(Thread,5000);
CloseHandle(Thread);

costtime= (float)(end - start) / CLOCKS_PER_SEC; //转换时间格式
printf("Cost time:%f Sec",costtime);//显示耗时

//退出前清理
if(sockRaw != INVALID_SOCKET) closesocket(sockRaw);
WSACleanup();
return 0;