1/*	$NetBSD: ln.c,v 1.40 2018/08/26 23:01:06 sevan Exp $	*/
2
3/*-
4 * Copyright (c) 1987, 1993, 1994
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#if 0
33#ifndef lint
34static char const copyright[] =
35"@(#) Copyright (c) 1987, 1993, 1994\n\
36	The Regents of the University of California.  All rights reserved.\n";
37#endif /* not lint */
38
39#ifndef lint
40static char sccsid[] = "@(#)ln.c	8.2 (Berkeley) 3/31/94";
41#endif /* not lint */
42#endif
43#include <sys/cdefs.h>
44#ifdef __FBSDID
45__FBSDID("$FreeBSD: head/bin/ln/ln.c 251261 2013-06-02 17:55:00Z eadler $");
46#endif
47__RCSID("$NetBSD: ln.c,v 1.40 2018/08/26 23:01:06 sevan Exp $");
48
49#include <sys/param.h>
50#include <sys/stat.h>
51
52#include <err.h>
53#include <errno.h>
54#include <fcntl.h>
55#include <libgen.h>
56#include <limits.h>
57#include <stdio.h>
58#include <stdlib.h>
59#include <string.h>
60#include <unistd.h>
61
62static int	fflag;			/* Unlink existing files. */
63static int	Fflag;			/* Remove empty directories also. */
64static int	hflag;			/* Check new name for symlink first. */
65static int	iflag;			/* Interactive mode. */
66static int	Pflag;			/* Create hard links to symlinks. */
67static int	sflag;			/* Symbolic, not hard, link. */
68static int	vflag;			/* Verbose output. */
69static int	wflag;			/* Warn if symlink target does not
70					 * exist, and -f is not enabled. */
71static char	linkch;
72
73static int	linkit(const char *, const char *, int);
74static __dead void	usage(void);
75
76int
77main(int argc, char *argv[])
78{
79	struct stat sb;
80	char *p, *targetdir;
81	int ch, exitval;
82
83	/*
84	 * Test for the special case where the utility is called as
85	 * "link", for which the functionality provided is greatly
86	 * simplified.
87	 */
88	if ((p = strrchr(argv[0], '/')) == NULL)
89		p = argv[0];
90	else
91		++p;
92	if (strcmp(p, "link") == 0) {
93		while (getopt(argc, argv, "") != -1)
94			usage();
95		argc -= optind;
96		argv += optind;
97		if (argc != 2)
98			usage();
99		if (link(argv[0], argv[1]) == -1)
100			err(EXIT_FAILURE, NULL);
101		exit(EXIT_SUCCESS);
102	}
103
104	while ((ch = getopt(argc, argv, "FLPfhinsvw")) != -1)
105		switch (ch) {
106		case 'F':
107			Fflag = 1;
108			break;
109		case 'L':
110			Pflag = 0;
111			break;
112		case 'P':
113			Pflag = 1;
114			break;
115		case 'f':
116			fflag = 1;
117			iflag = 0;
118			wflag = 0;
119			break;
120		case 'h':
121		case 'n':
122			hflag = 1;
123			break;
124		case 'i':
125			iflag = 1;
126			fflag = 0;
127			break;
128		case 's':
129			sflag = 1;
130			break;
131		case 'v':
132			vflag = 1;
133			break;
134		case 'w':
135			wflag = 1;
136			break;
137		case '?':
138		default:
139			usage();
140		}
141
142	argv += optind;
143	argc -= optind;
144
145	linkch = sflag ? '-' : '=';
146	if (sflag == 0)
147		Fflag = 0;
148	if (Fflag == 1 && iflag == 0) {
149		fflag = 1;
150		wflag = 0;		/* Implied when fflag != 0 */
151	}
152
153	switch(argc) {
154	case 0:
155		usage();
156		/* NOTREACHED */
157	case 1:				/* ln source */
158		exit(linkit(argv[0], ".", 1));
159	case 2:				/* ln source target */
160		exit(linkit(argv[0], argv[1], 0));
161	default:
162		;
163	}
164					/* ln source1 source2 directory */
165	targetdir = argv[argc - 1];
166	if (hflag && lstat(targetdir, &sb) == 0 && S_ISLNK(sb.st_mode)) {
167		/*
168		 * We were asked not to follow symlinks, but found one at
169		 * the target--simulate "not a directory" error
170		 */
171		errno = ENOTDIR;
172		err(1, "%s", targetdir);
173	}
174	if (stat(targetdir, &sb))
175		err(1, "%s", targetdir);
176	if (!S_ISDIR(sb.st_mode))
177		usage();
178	for (exitval = 0; *argv != targetdir; ++argv)
179		exitval |= linkit(*argv, targetdir, 1);
180	exit(exitval);
181}
182
183/*
184 * Two pathnames refer to the same directory entry if the directories match
185 * and the final components' names match.
186 */
187static int
188samedirent(const char *path1, const char *path2)
189{
190	const char *file1, *file2;
191	char pathbuf[PATH_MAX];
192	struct stat sb1, sb2;
193
194	if (strcmp(path1, path2) == 0)
195		return 1;
196	file1 = strrchr(path1, '/');
197	if (file1 != NULL)
198		file1++;
199	else
200		file1 = path1;
201	file2 = strrchr(path2, '/');
202	if (file2 != NULL)
203		file2++;
204	else
205		file2 = path2;
206	if (strcmp(file1, file2) != 0)
207		return 0;
208	if (file1 - path1 >= PATH_MAX || file2 - path2 >= PATH_MAX)
209		return 0;
210	if (file1 == path1)
211		memcpy(pathbuf, ".", 2);
212	else {
213		memcpy(pathbuf, path1, file1 - path1);
214		pathbuf[file1 - path1] = '\0';
215	}
216	if (stat(pathbuf, &sb1) != 0)
217		return 0;
218	if (file2 == path2)
219		memcpy(pathbuf, ".", 2);
220	else {
221		memcpy(pathbuf, path2, file2 - path2);
222		pathbuf[file2 - path2] = '\0';
223	}
224	if (stat(pathbuf, &sb2) != 0)
225		return 0;
226	return sb1.st_dev == sb2.st_dev && sb1.st_ino == sb2.st_ino;
227}
228
229static int
230linkit(const char *source, const char *target, int isdir)
231{
232	struct stat sb;
233	const char *p;
234	int ch, exists, first;
235	char path[PATH_MAX];
236	char wbuf[PATH_MAX];
237	char bbuf[PATH_MAX];
238
239	if (!sflag) {
240		/* If source doesn't exist, quit now. */
241		if ((Pflag ? lstat : stat)(source, &sb)) {
242			warn("%s", source);
243			return (1);
244		}
245		/* Only symbolic links to directories. */
246		if (S_ISDIR(sb.st_mode)) {
247			errno = EISDIR;
248			warn("%s", source);
249			return (1);
250		}
251	}
252
253	/*
254	 * If the target is a directory (and not a symlink if hflag),
255	 * append the source's name.
256	 */
257	if (isdir ||
258	    (lstat(target, &sb) == 0 && S_ISDIR(sb.st_mode)) ||
259	    (!hflag && stat(target, &sb) == 0 && S_ISDIR(sb.st_mode))) {
260		if (strlcpy(bbuf, source, sizeof(bbuf)) >= sizeof(bbuf) ||
261		    (p = basename(bbuf)) == NULL ||
262		    snprintf(path, sizeof(path), "%s/%s", target, p) >=
263		    (ssize_t)sizeof(path)) {
264			errno = ENAMETOOLONG;
265			warn("%s", source);
266			return (1);
267		}
268		target = path;
269	}
270
271	/*
272	 * If the link source doesn't exist, and a symbolic link was
273	 * requested, and -w was specified, give a warning.
274	 */
275	if (sflag && wflag) {
276		if (*source == '/') {
277			/* Absolute link source. */
278			if (stat(source, &sb) != 0)
279				 warn("warning: %s inaccessible", source);
280		} else {
281			/*
282			 * Relative symlink source.  Try to construct the
283			 * absolute path of the source, by appending `source'
284			 * to the parent directory of the target.
285			 */
286			strlcpy(bbuf, target, sizeof(bbuf));
287			p = dirname(bbuf);
288			if (p != NULL) {
289				(void)snprintf(wbuf, sizeof(wbuf), "%s/%s",
290						p, source);
291				if (stat(wbuf, &sb) != 0)
292					warn("warning: %s", source);
293			}
294		}
295	}
296
297	/*
298	 * If the file exists, first check it is not the same directory entry.
299	 */
300	exists = !lstat(target, &sb);
301	if (exists) {
302		if (!sflag && samedirent(source, target)) {
303			warnx("%s and %s are the same directory entry",
304			    source, target);
305			return (1);
306		}
307	}
308	/*
309	 * Then unlink it forcibly if -f was specified
310	 * and interactively if -i was specified.
311	 */
312	if (fflag && exists) {
313		if (Fflag && S_ISDIR(sb.st_mode)) {
314			if (rmdir(target)) {
315				warn("%s", target);
316				return (1);
317			}
318		} else if (unlink(target)) {
319			warn("%s", target);
320			return (1);
321		}
322	} else if (iflag && exists) {
323		fflush(stdout);
324		fprintf(stderr, "replace %s? ", target);
325
326		first = ch = getchar();
327		while(ch != '\n' && ch != EOF)
328			ch = getchar();
329		if (first != 'y' && first != 'Y') {
330			fprintf(stderr, "not replaced\n");
331			return (1);
332		}
333
334		if (Fflag && S_ISDIR(sb.st_mode)) {
335			if (rmdir(target)) {
336				warn("%s", target);
337				return (1);
338			}
339		} else if (unlink(target)) {
340			warn("%s", target);
341			return (1);
342		}
343	}
344
345	/* Attempt the link. */
346	if (sflag ? symlink(source, target) :
347	    linkat(AT_FDCWD, source, AT_FDCWD, target,
348	    Pflag ? 0 : AT_SYMLINK_FOLLOW)) {
349		warn("%s", target);
350		return (1);
351	}
352	if (vflag)
353		(void)printf("%s %c> %s\n", target, linkch, source);
354	return (0);
355}
356
357static __dead void
358usage(void)
359{
360	(void)fprintf(stderr,
361	    "usage: %s [-L | -P | -s [-F]] [-f | -iw] [-hnv] source_file [target_file]\n"
362	    "       %s [-L | -P | -s [-F]] [-f | -iw] [-hnv] source_file ... target_dir\n"
363	    "       link source_file target_file\n", getprogname(), getprogname());
364	exit(1);
365}
366