协议名称处理函数xxxprotoxxx（）

#include <netdb.h>
#include <stdio.h>

void
display_protocol(struct protoent *pt)
{
    int i = 0;
    
    if(pt)
    {
        printf("protocol name: %s", pt->p_name);
        if(pt->p_aliases)
        {
            printf("alias name:");
            while(pt->p_aliases[i])
            {
                printf("%s ", pt->p_aliases[i]);
                i++;
            }
        }
        printf(", value: %d\n", pt->p_proto);
    }
}


int
main(int argc, char **argv)
{    
    int i = 0;
    
    const char *const protocol_name[] = { "ip", "icmp", "tcp", "udp", NULL };
    
    setprotoent(1);
    while(protocol_name[i] != NULL)
    {
        struct protoent *pt = getprotobyname((const char *)&protocol_name[i][0]);
        if(pt)
        {
            display_protocol(pt);
        }
        i++;
    }
    endprotoent();
    return(0);
}