ln.c revision 321094 
1/*-
2 * Copyright (c) 1987, 1993, 1994
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#if 0
31#ifndef lint
32static char const copyright[] =
33"@(#) Copyright (c) 1987, 1993, 1994\n\
34	The Regents of the University of California.  All rights reserved.\n";
35#endif /* not lint */
36
37#ifndef lint
38static char sccsid[] = "@(#)ln.c	8.2 (Berkeley) 3/31/94";
39#endif /* not lint */
40#endif
41#include <sys/cdefs.h>
42__FBSDID("$FreeBSD: stable/10/bin/ln/ln.c 321094 2017-07-17 21:13:43Z ngie $");
43
44#include <sys/param.h>
45#include <sys/stat.h>
46
47#include <err.h>
48#include <errno.h>
49#include <fcntl.h>
50#include <libgen.h>
51#include <limits.h>
52#include <stdio.h>
53#include <stdlib.h>
54#include <string.h>
55#include <unistd.h>
56
57static int	fflag;			/* Unlink existing files. */
58static int	Fflag;			/* Remove empty directories also. */
59static int	hflag;			/* Check new name for symlink first. */
60static int	iflag;			/* Interactive mode. */
61static int	Pflag;			/* Create hard links to symlinks. */
62static int	sflag;			/* Symbolic, not hard, link. */
63static int	vflag;			/* Verbose output. */
64static int	wflag;			/* Warn if symlink target does not
65					 * exist, and -f is not enabled. */
66static char	linkch;
67
68static int	linkit(const char *, const char *, int);
69static void	usage(void);
70
71int
72main(int argc, char *argv[])
73{
74	struct stat sb;
75	char *p, *targetdir;
76	int ch, exitval;
77
78	/*
79	 * Test for the special case where the utility is called as
80	 * "link", for which the functionality provided is greatly
81	 * simplified.
82	 */
83	if ((p = strrchr(argv[0], '/')) == NULL)
84		p = argv[0];
85	else
86		++p;
87	if (strcmp(p, "link") == 0) {
88		while (getopt(argc, argv, "") != -1)
89			usage();
90		argc -= optind;
91		argv += optind;
92		if (argc != 2)
93			usage();
94		exit(linkit(argv[0], argv[1], 0));
95	}
96
97	while ((ch = getopt(argc, argv, "FLPfhinsvw")) != -1)
98		switch (ch) {
99		case 'F':
100			Fflag = 1;
101			break;
102		case 'L':
103			Pflag = 0;
104			break;
105		case 'P':
106			Pflag = 1;
107			break;
108		case 'f':
109			fflag = 1;
110			iflag = 0;
111			wflag = 0;
112			break;
113		case 'h':
114		case 'n':
115			hflag = 1;
116			break;
117		case 'i':
118			iflag = 1;
119			fflag = 0;
120			break;
121		case 's':
122			sflag = 1;
123			break;
124		case 'v':
125			vflag = 1;
126			break;
127		case 'w':
128			wflag = 1;
129			break;
130		case '?':
131		default:
132			usage();
133		}
134
135	argv += optind;
136	argc -= optind;
137
138	linkch = sflag ? '-' : '=';
139	if (sflag == 0)
140		Fflag = 0;
141	if (Fflag == 1 && iflag == 0) {
142		fflag = 1;
143		wflag = 0;		/* Implied when fflag != 0 */
144	}
145
146	switch(argc) {
147	case 0:
148		usage();
149		/* NOTREACHED */
150	case 1:				/* ln source */
151		exit(linkit(argv[0], ".", 1));
152	case 2:				/* ln source target */
153		exit(linkit(argv[0], argv[1], 0));
154	default:
155		;
156	}
157					/* ln source1 source2 directory */
158	targetdir = argv[argc - 1];
159	if (hflag && lstat(targetdir, &sb) == 0 && S_ISLNK(sb.st_mode)) {
160		/*
161		 * We were asked not to follow symlinks, but found one at
162		 * the target--simulate "not a directory" error
163		 */
164		errno = ENOTDIR;
165		err(1, "%s", targetdir);
166	}
167	if (stat(targetdir, &sb))
168		err(1, "%s", targetdir);
169	if (!S_ISDIR(sb.st_mode))
170		usage();
171	for (exitval = 0; *argv != targetdir; ++argv)
172		exitval |= linkit(*argv, targetdir, 1);
173	exit(exitval);
174}
175
176/*
177 * Two pathnames refer to the same directory entry if the directories match
178 * and the final components' names match.
179 */
180static int
181samedirent(const char *path1, const char *path2)
182{
183	const char *file1, *file2;
184	char pathbuf[PATH_MAX];
185	struct stat sb1, sb2;
186
187	if (strcmp(path1, path2) == 0)
188		return 1;
189	file1 = strrchr(path1, '/');
190	if (file1 != NULL)
191		file1++;
192	else
193		file1 = path1;
194	file2 = strrchr(path2, '/');
195	if (file2 != NULL)
196		file2++;
197	else
198		file2 = path2;
199	if (strcmp(file1, file2) != 0)
200		return 0;
201	if (file1 - path1 >= PATH_MAX || file2 - path2 >= PATH_MAX)
202		return 0;
203	if (file1 == path1)
204		memcpy(pathbuf, ".", 2);
205	else {
206		memcpy(pathbuf, path1, file1 - path1);
207		pathbuf[file1 - path1] = '\0';
208	}
209	if (stat(pathbuf, &sb1) != 0)
210		return 0;
211	if (file2 == path2)
212		memcpy(pathbuf, ".", 2);
213	else {
214		memcpy(pathbuf, path2, file2 - path2);
215		pathbuf[file2 - path2] = '\0';
216	}
217	if (stat(pathbuf, &sb2) != 0)
218		return 0;
219	return sb1.st_dev == sb2.st_dev && sb1.st_ino == sb2.st_ino;
220}
221
222static int
223linkit(const char *source, const char *target, int isdir)
224{
225	struct stat sb;
226	const char *p;
227	int ch, exists, first;
228	char path[PATH_MAX];
229	char wbuf[PATH_MAX];
230	char bbuf[PATH_MAX];
231
232	if (!sflag) {
233		/* If source doesn't exist, quit now. */
234		if ((Pflag ? lstat : stat)(source, &sb)) {
235			warn("%s", source);
236			return (1);
237		}
238		/* Only symbolic links to directories. */
239		if (S_ISDIR(sb.st_mode)) {
240			errno = EISDIR;
241			warn("%s", source);
242			return (1);
243		}
244	}
245
246	/*
247	 * If the target is a directory (and not a symlink if hflag),
248	 * append the source's name, unless Fflag is set.
249	 */
250	if (!Fflag && (isdir ||
251	    (lstat(target, &sb) == 0 && S_ISDIR(sb.st_mode)) ||
252	    (!hflag && stat(target, &sb) == 0 && S_ISDIR(sb.st_mode)))) {
253		if (strlcpy(bbuf, source, sizeof(bbuf)) >= sizeof(bbuf) ||
254		    (p = basename(bbuf)) == NULL ||
255		    snprintf(path, sizeof(path), "%s/%s", target, p) >=
256		    (ssize_t)sizeof(path)) {
257			errno = ENAMETOOLONG;
258			warn("%s", source);
259			return (1);
260		}
261		target = path;
262	}
263
264	/*
265	 * If the link source doesn't exist, and a symbolic link was
266	 * requested, and -w was specified, give a warning.
267	 */
268	if (sflag && wflag) {
269		if (*source == '/') {
270			/* Absolute link source. */
271			if (stat(source, &sb) != 0)
272				 warn("warning: %s inaccessible", source);
273		} else {
274			/*
275			 * Relative symlink source.  Try to construct the
276			 * absolute path of the source, by appending `source'
277			 * to the parent directory of the target.
278			 */
279			strlcpy(bbuf, target, sizeof(bbuf));
280			p = dirname(bbuf);
281			if (p != NULL) {
282				(void)snprintf(wbuf, sizeof(wbuf), "%s/%s",
283						p, source);
284				if (stat(wbuf, &sb) != 0)
285					warn("warning: %s", source);
286			}
287		}
288	}
289
290	/*
291	 * If the file exists, first check it is not the same directory entry.
292	 */
293	exists = !lstat(target, &sb);
294	if (exists) {
295		if (!sflag && samedirent(source, target)) {
296			warnx("%s and %s are the same directory entry",
297			    source, target);
298			return (1);
299		}
300	}
301	/*
302	 * Then unlink it forcibly if -f was specified
303	 * and interactively if -i was specified.
304	 */
305	if (fflag && exists) {
306		if (Fflag && S_ISDIR(sb.st_mode)) {
307			if (rmdir(target)) {
308				warn("%s", target);
309				return (1);
310			}
311		} else if (unlink(target)) {
312			warn("%s", target);
313			return (1);
314		}
315	} else if (iflag && exists) {
316		fflush(stdout);
317		fprintf(stderr, "replace %s? ", target);
318
319		first = ch = getchar();
320		while(ch != '\n' && ch != EOF)
321			ch = getchar();
322		if (first != 'y' && first != 'Y') {
323			fprintf(stderr, "not replaced\n");
324			return (1);
325		}
326
327		if (Fflag && S_ISDIR(sb.st_mode)) {
328			if (rmdir(target)) {
329				warn("%s", target);
330				return (1);
331			}
332		} else if (unlink(target)) {
333			warn("%s", target);
334			return (1);
335		}
336	}
337
338	/* Attempt the link. */
339	if (sflag ? symlink(source, target) :
340	    linkat(AT_FDCWD, source, AT_FDCWD, target,
341	    Pflag ? 0 : AT_SYMLINK_FOLLOW)) {
342		warn("%s", target);
343		return (1);
344	}
345	if (vflag)
346		(void)printf("%s %c> %s\n", target, linkch, source);
347	return (0);
348}
349
350static void
351usage(void)
352{
353	(void)fprintf(stderr, "%s\n%s\n%s\n",
354	    "usage: ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file [target_file]",
355	    "       ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file ... target_dir",
356	    "       link source_file target_file");
357	exit(1);
358}
359