Linux C实现FTP客户端的程序

#include "sys/types.h"
#include "sys/socket.h"
#include "netinet/in.h"
#include "arpa/inet.h"
#include "fcntl.h"
#include "unistd.h"
#include "stdarg.h"
#include "stdio.h"
#include "netdb.h"
int verbose = 1;
FILE *ftpio = NULL;
char buf[4096];
int ftpcmd(int sockftp,char *fmt,...)
{        
va_list vp;        
int err,len;        
if (ftpio == NULL) 
{                
ftpio = fdopen(sockftp,"r");                
if (ftpio == NULL)                        
return -1;        
}        
if (fmt) 
{                
va_start(vp,fmt);                
len = vsprintf(buf,fmt,vp);                
buf[len++] = '\r'; 
buf[len++]='\n';                
write(sockftp,buf,len);                
if (verbose)                        

write(1,buf,len);        
}        
do 
{                
   if (fgets(buf,sizeof(buf),ftpio) == NULL)                        
   return -1;                
   if (verbose)                        
   printf(buf);        
} while(buf[3] == '-');        
sscanf(buf,"%d",&err);        
return err;}

int ftp(char *host,char *user,char *pass,char *filename,char *savefile)
{        
int sockftp = -1,sockdata = -1,sockxfer = -1;        
struct sockaddr_in addr;        
unsigned long hostip;        
int len,tmp,err;        
int retval = -1;        
int savefd;        
unsigned char *c,*p;        
struct hostent *he;        
hostip = inet_addr(host);        
if (hostip == -1) 
{                
he = gethostbyname(host);                
if (he == NULL)                        
return -1;               
 hostip = * (unsigned long *)he->h_addr;        
}