source: trunk/minix/commands/simple/write.c@ 11

/* write - write to a logged in user    Authors: N. Andrew and F. van Kempen */

/*
 * Usage:       write [-c] [-v] user [tty]
 *                      -c Read & write one character at a time (cbreak mode)
 *                      -v Verbose
 *
 * Version:     1.6     10/24/92
 *
 * NOTES:       Write requires 1.4a (or higher) libraries,
 *              for getopt(), strchr().
 *
 * Authors:     Nick Andrew  (nick@nswitgould.oz)  - Public Domain
 *              Fred van Kempen (minixug!waltje@kyber.uucp)
 */

#include <sys/types.h>
#include <fcntl.h>
#include <pwd.h>
#include <termios.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>
#include <time.h>
#include <stdio.h>
#include <minix/paths.h>

static char *Version = "@(#) WRITE 1.6 (10/24/92)";

int otty;                       /* file desc of callee's terminal */
short int cbreak = 0;           /* are we in CBREAK (-c) mode? */
short int verbose = 0;          /* are we in VERBOSE (-v) mode? */
short int writing = 0;          /* is there a connection? */
char *user = NULL;      /* callee's user name */
char *tty = NULL;       /* callee's terminal if given */
char *ourtty = NULL;    /* our terminal name */
struct termios ttyold, ttynew;  /* our tty controlling structs */

extern int optind;

_PROTOTYPE(int main, (int argc, char **argv));
_PROTOTYPE(char *finduser, (void));
_PROTOTYPE(void settty, (char *utty));
_PROTOTYPE(void sayhello, (void));
_PROTOTYPE(void escape, (char *cmd));
_PROTOTYPE(void writetty, (void));
_PROTOTYPE(void usage, (void));
_PROTOTYPE(void intr, (int dummy));

char *finduser()
{
/* Search the UTMP database for the user we want. */

  static char utmptty[16];
  struct utmp utmp;
  struct passwd *userptr;
  int utmpfd;

  ourtty = ttyname(0);
  if (ourtty == NULL) ourtty = "/dev/console";

  if (user == NULL) exit(-1);
  if ((userptr = getpwnam(user)) == NULL) {
        fprintf(stderr, "No such user: %s\n", user);
        return(NULL);
  }
  if (verbose) fprintf(stderr, "Trying to write to %s\n",
                userptr->pw_gecos);

  if ((utmpfd = open(_PATH_UTMP, O_RDONLY)) < 0) {
        fprintf(stderr, "Cannot open utmp file\n");
        return(NULL);
  }
  utmptty[0] = '\0';

  /* We want to find if 'user' is logged on, and return in utmptty[]
   * 'user' `s terminal, and if 'user' is logged onto the tty the
   * caller specified, return that tty name. */
  while (read(utmpfd, (char *) &utmp, sizeof(utmp)) == sizeof(utmp)) {
        /* is this the user we are looking for? */
        if (strncmp(utmp.ut_name, user, sizeof(utmp.ut_name))) continue;

        strcpy(utmptty, utmp.ut_line);
        /* is he on the terminal we want to write to? */
        if (tty == NULL || !strcmp(utmptty, tty)) {
                break;
        }
  }

  if (utmptty[0] == '\0') {
        fprintf(stderr, "%s is not logged on\n", user);
        return( NULL);
  }
  if (tty != NULL && strcmp(utmptty, tty)) {
        fprintf(stderr, "%s is logged onto %s, not %s\n", user, utmptty, tty);
        return( NULL);
  }
  close(utmpfd);

  if (verbose) fprintf(stderr, "Writing to %s on %s\n", user, utmptty);
  return(utmptty);
}


void settty(utty)
char *utty;                     /* name of terminal found in utmp */
{
/* Open other person's terminal and setup our own terminal. */

  char buff[48];

  sprintf(buff, "/dev/%s", utty);
  if ((otty = open(buff, O_WRONLY)) < 0) {
        fprintf(stderr, "Cannot open %s to write to %s\n", utty, user);
        fprintf(stderr, "It may have write permission turned off\n");
        exit(-1);
  }
  tcgetattr(0, &ttyold);
  tcgetattr(0, &ttynew);
  ttynew.c_lflag &= ~(ICANON|ECHO);
  signal(SIGINT, intr);
  if (cbreak) tcsetattr(0, TCSANOW, &ttynew);
}


void sayhello()
{
  struct passwd *pw;
  char buff[128];
  long now;
  char *sp;

  time(&now);

  pw = getpwuid(getuid());
  if (pw == NULL) {
        fprintf(stderr, "unknown user\n");
        exit(-1);
  }
  if ((sp = strrchr(ourtty, '/')) != NULL)
        ++sp;
  else
        sp = ourtty;

  sprintf(buff, "\nMessage from %s (%s) %-24.24s...\n",
        pw->pw_name, sp, ctime(&now));

  write(otty, buff, strlen(buff));
  printf("\007\007");
  fflush(stdout);
}


void escape(cmd)
char *cmd;
{
/* Shell escape. */

  register char *x;

  write(1, "!\n", 2);
  for (x = cmd; *x; ++x)
        if (*x == '\n') *x = '\0';

  system(cmd);
  write(1, "!\n", 2);
}


void writetty()
{
/* The write loop. */

  char line[80];
  int n, cb_esc;

  writing = 1;
  cb_esc = 0;

  while ((n = read(0, line, 79)) > 0) {
        if (line[0] == '\004') break;   /* EOT */

        if (cbreak && line[0] == '\n') cb_esc = 1;

        if (cbreak) write(1, line, n);

        if (line[0] == '!') {
                if (cbreak && cb_esc) {
                        cb_esc = 0;
                        tcsetattr(0, TCSANOW, &ttyold);
                        read(0, line, 79);
                        escape(line);
                        tcsetattr(0, TCSANOW, &ttynew);
                } else if (cbreak)
                        write(otty, line, n);
                else
                        escape(&line[1]);
                continue;
        }
        write(otty, line, n);
  }
  write(1, "\nEOT\n", 5);
  write(otty, "\nEOT\n", 5);
}


void usage()
{
  fprintf(stderr, "usage: write [-c] [-v] user [tty]\n");
  fprintf(stderr, "\t-c : cbreak mode\n\t-v : verbose\n");
  exit(-1);
}


int main(argc, argv)
int argc;
char *argv[];
{
  register int c;
  char *sp;

  setbuf(stdout, (char *) NULL);

  /* Parse options. */
  while ((c = getopt(argc, argv, "cv")) != EOF) switch (c) {
                case 'c':       cbreak = 1;     break;
                case 'v':       verbose = 1;    break;
            default:
                usage();
        }

  /* Parse user and tty arguments */
  if (optind < argc) {
        user = argv[optind++];

        /* WTMP usernames are 1-8 chars */
        if (strlen(user) > 8) *(user + 8) = '\0';

        if (optind < argc) {
                tty = argv[optind++];
                if (optind < argc) usage();
        }
  } else
        usage();

  sp = finduser();              /* find which tty to write onto */
  if (sp != NULL) {     /* did we find one? */
        settty(sp);             /* setup our terminal */
        sayhello();             /* print the initial message */
        writetty();             /* the write loop */
        tcsetattr(0, TCSANOW, &ttyold);
        exit(0);
  }
  return(-1);
}

void intr(dummy)
int dummy;                      /* to satisfy the prototype */
{
/* The interrupt key has been hit. exit cleanly. */

  signal(SIGINT, SIG_IGN);
  fprintf(stderr, "\nInterrupt. Exiting write\n");
  tcsetattr(0, TCSANOW, &ttyold);
  if (writing) write(otty, "\nEOT\n", 5);
  exit(0);
}