#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
main(int a, char **v){struct sockaddr_in h;int s;char c[1024];
bzero(&h,sizeof(h));h.sin_family=AF_INET;h.sin_port=htons(21);inet_aton(v[1],&h.sin_addr);
s=socket(AF_INET,SOCK_STREAM,0);connect(s,(struct sockaddr *)&h,sizeof(h));
read(s,c,1024);write(s,v[2],strlen(v[2]));write(s,"\r\n",2);read(s,c,1024);
write(s,v[3],strlen(v[3]));write(s,"\r\n",2);read(s,c,1024);while(1){
printf("$: ");fgets(c,1024,stdin);write(s,c,strlen(c));write(s,"\r\n",2);
read(s,c,1024);printf("%s", c);}close(s);}

7行じゃないけど。ｆｔｐもどき
./a.out 127.0.0.1 "USER user" "PASS password"
$:の後にコマンドです。