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write.c
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C/C++ Source or Header
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1990-07-23
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6KB
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261 lines
/* 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: 1.5 01/09/90
*
* 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 <sgtty.h>
#include <signal.h>
#include <string.h>
#include <time.h>
#include <utmp.h>
#include <unistd.h>
#include <stdio.h>
static char *Version = "@(#) WRITE 1.5 (01/09/90)";
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 sgttyb ttyold, ttynew; /* our tty controlling structs */
extern int getopt(), optind; /* from getopt(3) */
void intr();
char *finduser()
{
/* Search the UTMP database for the user we want. */
static char utmptty[16];
struct utmp utmp;
struct passwd *userptr;
char ourname[9];
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(UTMP, O_RDONLY)) < 0) {
fprintf(stderr, "Cannot open utmp file\n");
return((char *) 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 (strcmp(utmp.ut_name, user)) continue;
/* is he on the terminal we want to write to? */
if (tty == NULL || strcmp(utmptty, tty)) {
strcpy(utmptty, utmp.ut_line);
break;
}
}
if (utmptty[0] == '\0') {
fprintf(stderr, "%s is not logged on\n", user);
return( (char *) NULL);
}
if (tty != NULL && strcmp(utmptty, tty)) {
fprintf(stderr, "%s is logged onto %s, not %s\n", user, utmptty, tty);
return( (char *) 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);
}
ioctl(0, TIOCGETP, &ttyold);
ioctl(0, TIOCGETP, &ttynew);
ttynew.sg_flags |= CBREAK;
signal(SIGINT, intr);
if (cbreak) ioctl(0, TIOCSETP, &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 (line[0] == '!') {
if (cbreak && cb_esc) {
cb_esc = 0;
ioctl(0, TIOCSETP, &ttyold);
read(0, line, 79);
escape(line);
ioctl(0, TIOCSETP, &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);
}
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 */
ioctl(0, TIOCSETP, &ttyold);
exit(0);
}
exit(-1);
}
void intr()
{
/* The interrupt key has been hit. exit cleanly. */
signal(SIGINT, SIG_IGN);
fprintf(stderr, "\nInterrupt. Exiting write\n");
ioctl(0, TIOCSETP, &ttyold);
if (writing) write(otty, "\nEOT\n", 5);
exit(0);
}