#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define FINGER_PORT 79
#define bzero(ptr, size) memset (ptr, 0, size)

/* Create a TCP connection to host and port.  Returns a file
 * descriptor on success, -1 on error. */
int
tcpconnect (char *host, int port)
{
  struct hostent *h;
  struct sockaddr_in sa;
  int s;

  /* Get the address of the host at which to finger from the
   * hostname.  */
  h = gethostbyname (host);
  if (!h || h->h_length != sizeof (struct in_addr)) {
    fprintf (stderr, "%s: no such host\n", host);
    return -1;
  }

  /* Create a TCP socket. */
  s = socket (AF_INET, SOCK_STREAM, 0);

  /* Use bind to set an address and port number for our end of the
   * finger TCP connection. */
  bzero (&sa, sizeof (sa));
  sa.sin_family = AF_INET;
  sa.sin_port = htons (0);                  /* tells OS to choose a port */
  sa.sin_addr.s_addr = htonl (INADDR_ANY);  /* tells OS to choose IP addr */
  if (bind (s, (struct sockaddr *) &sa, sizeof (sa)) < 0) {
    perror ("bind");
    close (s);
    return -1;
  }

  /* Now use h to set set the destination address. */
  sa.sin_port = htons (port);
  sa.sin_addr = *(struct in_addr *) h->h_addr;

  /* And connect to the server */
  if (connect (s, (struct sockaddr *) &sa, sizeof (sa)) < 0) {
    perror (host);
    close (s);
    return -1;
  }

  return s;
}

int
main (int argc, char **argv)
{
  char *user;
  char *host;
  int s;
  int nread;
  char buf[1024];

  /* Get the name of the host at which to finger from the end of the
   * command line argument. */
  if (argc == 2) {
    user = malloc (1 + strlen (argv[1]));
    if (!user) {
      fprintf (stderr, "out of memory\n");
      exit (1);
    }
    strcpy (user, argv[1]);
    host = strrchr (user, '@');
  }
  else
    user = host = NULL;
  if (!host) {
    fprintf (stderr, "usage: %s user@host\n", argv[0]);
    exit (1);
  }
  *host++ = '\0';

  /* Try connecting to the host. */
  s = tcpconnect (host, FINGER_PORT);
  if (s < 0)
    exit (1);

  /* Send the username to finger */
  if (write (s, user, strlen (user)) < 0
      || write (s, "\r\n", 2) < 0) {
    perror (host);
    exit (1);
  }

  /* Now copy the result of the finger command to stdout. */
  while ((nread = read (s, buf, sizeof (buf))) > 0)
    write (1, buf, nread);

  exit (0);
}