#include <stdio.h>
#include <netdb.h>
int getport(char *port)
{
struct servent *sp;
sp = getservbyname(port, "tcp");
if (sp == NULL) {
return (atoi(port));
}
else {
return (ntohs(sp->s_port));
}
}
int main(int argc, char *argv[])
{
if( argc != 2) {
printf("Invalid argument \n");
exit(0);
}
printf("%d\n", getport(argv[1]) );
}
실행결과
실행결과
# getport 21
21
# getport ftp
21
# getport 23
23
# getport telnet
23
