NetBSD/usr.bin/write/write.c

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/* $NetBSD: write.c,v 1.16 1999/11/09 15:06:37 drochner Exp $ */
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/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
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*
* This code is derived from software contributed to Berkeley by
* Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
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#include <sys/cdefs.h>
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#ifndef lint
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__COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
The Regents of the University of California. All rights reserved.\n");
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#endif /* not lint */
#ifndef lint
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#if 0
static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95";
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#else
__RCSID("$NetBSD: write.c,v 1.16 1999/11/09 15:06:37 drochner Exp $");
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#endif
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#endif /* not lint */
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#include <sys/types.h>
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#include <sys/param.h>
#include <sys/stat.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>
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#include <signal.h>
#include <time.h>
#include <fcntl.h>
#include <pwd.h>
#include <unistd.h>
#include <utmp.h>
#include <err.h>
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void done __P((int));
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void do_write __P((char *, char *, uid_t));
void wr_fputs __P((char *));
void search_utmp __P((char *, char *, char *, uid_t, int));
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int term_chk __P((char *, int *, time_t *, int));
int utmp_chk __P((char *, char *));
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int main __P((int, char **));
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int
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main(argc, argv)
int argc;
char **argv;
{
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char *cp;
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time_t atime;
uid_t myuid;
int msgsok, myttyfd;
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char tty[MAXPATHLEN], *mytty;
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/* check that sender has write enabled */
if (isatty(fileno(stdin)))
myttyfd = fileno(stdin);
else if (isatty(fileno(stdout)))
myttyfd = fileno(stdout);
else if (isatty(fileno(stderr)))
myttyfd = fileno(stderr);
else
errx(1, "can't find your tty");
if (!(mytty = ttyname(myttyfd)))
errx(1, "can't find your tty's name");
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if ((cp = strrchr(mytty, '/')) != NULL)
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mytty = cp + 1;
if (term_chk(mytty, &msgsok, &atime, 1))
exit(1);
if (!msgsok) {
(void)fprintf(stderr,
"warning: you have write permission turned off; "
"no reply possible\n");
}
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myuid = getuid();
/* check args */
switch (argc) {
case 2:
search_utmp(argv[1], tty, mytty, myuid, sizeof tty);
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do_write(tty, mytty, myuid);
break;
case 3:
if (!strncmp(argv[2], "/dev/", 5))
argv[2] += 5;
if (utmp_chk(argv[1], argv[2]))
errx(1, "%s is not logged in on %s",
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argv[1], argv[2]);
if (term_chk(argv[2], &msgsok, &atime, 1))
exit(1);
if (myuid && !msgsok)
errx(1, "%s has messages disabled on %s",
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argv[1], argv[2]);
do_write(argv[2], mytty, myuid);
break;
default:
(void)fprintf(stderr, "usage: write user [tty]\n");
exit(1);
}
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done(0);
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/* NOTREACHED */
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#ifdef __GNUC__
return (0);
#endif
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}
/*
* utmp_chk - checks that the given user is actually logged in on
* the given tty
*/
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int
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utmp_chk(user, tty)
char *user, *tty;
{
struct utmp u;
int ufd;
if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
return(0); /* ignore error, shouldn't happen anyway */
while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
(void)close(ufd);
return(0);
}
(void)close(ufd);
return(1);
}
/*
* search_utmp - search utmp for the "best" terminal to write to
*
* Ignores terminals with messages disabled, and of the rest, returns
* the one with the most recent access time. Returns as value the number
* of the user's terminals with messages enabled, or -1 if the user is
* not logged in at all.
*
* Special case for writing to yourself - ignore the terminal you're
* writing from, unless that's the only terminal with messages enabled.
*/
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void
search_utmp(user, tty, mytty, myuid, ttylen)
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char *user, *tty, *mytty;
uid_t myuid;
int ttylen;
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{
struct utmp u;
time_t bestatime, atime;
int ufd, nloggedttys, nttys, msgsok, user_is_me;
char atty[UT_LINESIZE + 1];
if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
err(1, "%s", _PATH_UTMP);
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nloggedttys = nttys = 0;
bestatime = 0;
user_is_me = 0;
while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
++nloggedttys;
(void)strncpy(atty, u.ut_line, UT_LINESIZE);
atty[UT_LINESIZE] = '\0';
if (term_chk(atty, &msgsok, &atime, 0))
continue; /* bad term? skip */
if (myuid && !msgsok)
continue; /* skip ttys with msgs off */
if (strcmp(atty, mytty) == 0) {
user_is_me = 1;
continue; /* don't write to yourself */
}
++nttys;
if (atime > bestatime) {
bestatime = atime;
(void)strncpy(tty, atty, ttylen - 1);
tty[ttylen - 1] = '\0';
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}
}
(void)close(ufd);
if (nloggedttys == 0)
errx(1, "%s is not logged in", user);
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if (nttys == 0) {
if (user_is_me) { /* ok, so write to yourself! */
(void)strncpy(tty, mytty, ttylen - 1);
tty[ttylen - 1] = '\0';
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return;
}
errx(1, "%s has messages disabled", user);
} else if (nttys > 1)
warnx("%s is logged in more than once; writing to %s",
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user, tty);
}
/*
* term_chk - check that a terminal exists, and get the message bit
* and the access time
*/
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int
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term_chk(tty, msgsokP, atimeP, showerror)
char *tty;
int *msgsokP, showerror;
time_t *atimeP;
{
struct stat s;
char path[MAXPATHLEN];
(void)snprintf(path, sizeof path, "/dev/%s", tty);
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if (stat(path, &s) < 0) {
if (showerror)
warn("%s", path);
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return(1);
}
*msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
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*atimeP = s.st_atime;
return(0);
}
/*
* do_write - actually make the connection
*/
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void
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do_write(tty, mytty, myuid)
char *tty, *mytty;
uid_t myuid;
{
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const char *login;
char *nows;
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struct passwd *pwd;
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time_t now;
char path[MAXPATHLEN], host[MAXHOSTNAMELEN + 1], line[512];
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/* Determine our login name before the we reopen() stdout */
if ((login = getlogin()) == NULL) {
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if ((pwd = getpwuid(myuid)) != NULL)
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login = pwd->pw_name;
else login = "???";
}
(void)snprintf(path, sizeof path, "/dev/%s", tty);
if ((freopen(path, "w", stdout)) == NULL)
err(1, "%s", path);
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(void)signal(SIGINT, done);
(void)signal(SIGHUP, done);
/* print greeting */
if (gethostname(host, sizeof(host)) < 0)
(void)strncpy(host, "???", sizeof(host) - 1);
else
host[sizeof(host) - 1] = '\0';
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now = time((time_t *)NULL);
nows = ctime(&now);
nows[16] = '\0';
(void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
login, host, mytty, nows + 11);
while (fgets(line, sizeof(line), stdin) != NULL)
wr_fputs(line);
}
/*
* done - cleanup and exit
*/
void
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done(dummy)
int dummy;
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{
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(void)printf("EOF\r\n");
exit(0);
}
/*
* wr_fputs - like fputs(), but makes control characters visible and
* turns \n into \r\n
*/
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void
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wr_fputs(s)
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char *s;
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{
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char c;
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#define PUTC(c) if (putchar(c) == EOF) goto err;
for (; *s != '\0'; ++s) {
c = toascii(*s);
if (c == '\n') {
PUTC('\r');
PUTC('\n');
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} else if (!isprint((unsigned char)c) &&
!isspace((unsigned char)c) && c != '\007') {
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PUTC('^');
PUTC(c^0x40); /* DEL to ?, others to alpha */
} else
PUTC(c);
}
return;
err: err(1, NULL);
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#undef PUTC
}