1 files changed, 311 insertions, 0 deletions
diff --git a/usr.bin/write/write.c b/usr.bin/write/write.c
new file mode 100644
index 0000000..2008fd2
--- /dev/null
+++ b/usr.bin/write/write.c
@@ -0,0 +1,311 @@
+/*
+ * Copyright (c) 1989, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * 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.
+ * 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.
+ */
+
+#ifndef lint
+static const char copyright[] =
+"@(#) Copyright (c) 1989, 1993\n\
+	The Regents of the University of California.  All rights reserved.\n";
+#endif
+
+#if 0
+#ifndef lint
+static char sccsid[] = "@(#)write.c	8.1 (Berkeley) 6/6/93";
+#endif
+#endif
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/signal.h>
+#include <sys/stat.h>
+#include <sys/file.h>
+#include <sys/time.h>
+#include <ctype.h>
+#include <err.h>
+#include <locale.h>
+#include <paths.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <utmpx.h>
+#include <wchar.h>
+#include <wctype.h>
+
+void done(int);
+void do_write(char *, char *, uid_t);
+static void usage(void);
+int term_chk(char *, int *, time_t *, int);
+void wr_fputs(wchar_t *s);
+void search_utmp(char *, char *, char *, uid_t);
+int utmp_chk(char *, char *);
+
+int
+main(int argc, char **argv)
+{
+	time_t atime;
+	uid_t myuid;
+	int msgsok, myttyfd;
+	char tty[MAXPATHLEN], *mytty;
+
+	(void)setlocale(LC_CTYPE, "");
+
+	while (getopt(argc, argv, "") != -1)
+		usage();
+	argc -= optind;
+	argv += optind;
+
+	/* 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");
+	if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV)))
+		mytty += strlen(_PATH_DEV);
+	if (term_chk(mytty, &msgsok, &atime, 1))
+		exit(1);
+	if (!msgsok)
+		errx(1, "you have write permission turned off");
+
+	myuid = getuid();
+
+	/* check args */
+	switch (argc) {
+	case 1:
+		search_utmp(argv[0], tty, mytty, myuid);
+		do_write(tty, mytty, myuid);
+		break;
+	case 2:
+		if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV)))
+			argv[1] += strlen(_PATH_DEV);
+		if (utmp_chk(argv[0], argv[1]))
+			errx(1, "%s is not logged in on %s", argv[0], argv[1]);
+		if (term_chk(argv[1], &msgsok, &atime, 1))
+			exit(1);
+		if (myuid && !msgsok)
+			errx(1, "%s has messages disabled on %s", argv[0], argv[1]);
+		do_write(argv[1], mytty, myuid);
+		break;
+	default:
+		usage();
+	}
+	done(0);
+	return (0);
+}
+
+static void
+usage(void)
+{
+	(void)fprintf(stderr, "usage: write user [tty]\n");
+	exit(1);
+}
+
+/*
+ * utmp_chk - checks that the given user is actually logged in on
+ *     the given tty
+ */
+int
+utmp_chk(char *user, char *tty)
+{
+	struct utmpx lu, *u;
+
+	strncpy(lu.ut_line, tty, sizeof lu.ut_line);
+	setutxent();
+	while ((u = getutxline(&lu)) != NULL)
+		if (u->ut_type == USER_PROCESS &&
+		    strcmp(user, u->ut_user) == 0) {
+			endutxent();
+			return(0);
+		}
+	endutxent();
+	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.
+ */
+void
+search_utmp(char *user, char *tty, char *mytty, uid_t myuid)
+{
+	struct utmpx *u;
+	time_t bestatime, atime;
+	int nloggedttys, nttys, msgsok, user_is_me;
+
+	nloggedttys = nttys = 0;
+	bestatime = 0;
+	user_is_me = 0;
+
+	setutxent();
+	while ((u = getutxent()) != NULL)
+		if (u->ut_type == USER_PROCESS &&
+		    strcmp(user, u->ut_user) == 0) {
+			++nloggedttys;
+			if (term_chk(u->ut_line, &msgsok, &atime, 0))
+				continue;	/* bad term? skip */
+			if (myuid && !msgsok)
+				continue;	/* skip ttys with msgs off */
+			if (strcmp(u->ut_line, mytty) == 0) {
+				user_is_me = 1;
+				continue;	/* don't write to yourself */
+			}
+			++nttys;
+			if (atime > bestatime) {
+				bestatime = atime;
+				(void)strlcpy(tty, u->ut_line, MAXPATHLEN);
+			}
+		}
+	endutxent();
+
+	if (nloggedttys == 0)
+		errx(1, "%s is not logged in", user);
+	if (nttys == 0) {
+		if (user_is_me) {		/* ok, so write to yourself! */
+			(void)strlcpy(tty, mytty, MAXPATHLEN);
+			return;
+		}
+		errx(1, "%s has messages disabled", user);
+	} else if (nttys > 1) {
+		warnx("%s is logged in more than once; writing to %s", user, tty);
+	}
+}
+
+/*
+ * term_chk - check that a terminal exists, and get the message bit
+ *     and the access time
+ */
+int
+term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
+{
+	struct stat s;
+	char path[MAXPATHLEN];
+
+	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
+	if (stat(path, &s) < 0) {
+		if (showerror)
+			warn("%s", path);
+		return(1);
+	}
+	*msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0;	/* group write bit */
+	*atimeP = s.st_atime;
+	return(0);
+}
+
+/*
+ * do_write - actually make the connection
+ */
+void
+do_write(char *tty, char *mytty, uid_t myuid)
+{
+	const char *login;
+	char *nows;
+	struct passwd *pwd;
+	time_t now;
+	char path[MAXPATHLEN], host[MAXHOSTNAMELEN];
+	wchar_t line[512];
+
+	/* Determine our login name before we reopen() stdout */
+	if ((login = getlogin()) == NULL) {
+		if ((pwd = getpwuid(myuid)))
+			login = pwd->pw_name;
+		else
+			login = "???";
+	}
+
+	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
+	if ((freopen(path, "w", stdout)) == NULL)
+		err(1, "%s", path);
+
+	(void)signal(SIGINT, done);
+	(void)signal(SIGHUP, done);
+
+	/* print greeting */
+	if (gethostname(host, sizeof(host)) < 0)
+		(void)strcpy(host, "???");
+	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 (fgetws(line, sizeof(line)/sizeof(wchar_t), stdin) != NULL)
+		wr_fputs(line);
+}
+
+/*
+ * done - cleanup and exit
+ */
+void
+done(int n __unused)
+{
+	(void)printf("EOF\r\n");
+	exit(0);
+}
+
+/*
+ * wr_fputs - like fputs(), but makes control characters visible and
+ *     turns \n into \r\n
+ */
+void
+wr_fputs(wchar_t *s)
+{
+
+#define	PUTC(c)	if (putwchar(c) == WEOF) err(1, NULL);
+
+	for (; *s != L'\0'; ++s) {
+		if (*s == L'\n') {
+			PUTC(L'\r');
+			PUTC(L'\n');
+		} else if (iswprint(*s) || iswspace(*s)) {
+			PUTC(*s);
+		} else {
+			wprintf(L"<0x%X>", *s);
+		}
+	}
+	return;
+#undef PUTC
+}