realpath.c revision 111261 
1/*
2 * Copyright (c) 1994
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Jan-Simon Pendry.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38static char sccsid[] = "@(#)realpath.c	8.1 (Berkeley) 2/16/94";
39#endif /* LIBC_SCCS and not lint */
40#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: head/lib/libc/stdlib/realpath.c 111261 2003-02-22 18:08:34Z johan $");
42
43#include "namespace.h"
44#include <sys/param.h>
45#include <sys/stat.h>
46
47#include <errno.h>
48#include <fcntl.h>
49#include <stdlib.h>
50#include <string.h>
51#include <unistd.h>
52#include "un-namespace.h"
53
54/*
55 * char *realpath(const char *path, char resolved_path[PATH_MAX]);
56 *
57 * Find the real name of path, by removing all ".", ".." and symlink
58 * components.  Returns (resolved) on success, or (NULL) on failure,
59 * in which case the path which caused trouble is left in (resolved).
60 */
61char *
62realpath(path, resolved)
63	const char *path;
64	char *resolved;
65{
66	struct stat sb;
67	int fd, n, rootd, serrno;
68	char *p, *q, wbuf[PATH_MAX];
69	int symlinks = 0;
70
71	/* Save the starting point. */
72	if ((fd = _open(".", O_RDONLY)) < 0) {
73		(void)strcpy(resolved, ".");
74		return (NULL);
75	}
76
77	/*
78	 * Find the dirname and basename from the path to be resolved.
79	 * Change directory to the dirname component.
80	 * lstat the basename part.
81	 *     if it is a symlink, read in the value and loop.
82	 *     if it is a directory, then change to that directory.
83	 * get the current directory name and append the basename.
84	 */
85	(void)strlcpy(resolved, path, PATH_MAX);
86loop:
87	q = strrchr(resolved, '/');
88	if (q != NULL) {
89		p = q + 1;
90		if (q == resolved)
91			q = "/";
92		else {
93			do {
94				--q;
95			} while (q > resolved && *q == '/');
96			q[1] = '\0';
97			q = resolved;
98		}
99		if (chdir(q) < 0)
100			goto err1;
101	} else
102		p = resolved;
103
104	/* Deal with the last component. */
105	if (*p != '\0' && lstat(p, &sb) == 0) {
106		if (S_ISLNK(sb.st_mode)) {
107			if (++symlinks > MAXSYMLINKS) {
108				errno = ELOOP;
109				goto err1;
110			}
111			n = readlink(p, resolved, PATH_MAX - 1);
112			if (n < 0)
113				goto err1;
114			resolved[n] = '\0';
115			goto loop;
116		}
117		if (S_ISDIR(sb.st_mode)) {
118			if (chdir(p) < 0)
119				goto err1;
120			p = "";
121		}
122	}
123
124	/*
125	 * Save the last component name and get the full pathname of
126	 * the current directory.
127	 */
128	(void)strcpy(wbuf, p);
129	if (getcwd(resolved, PATH_MAX) == 0)
130		goto err1;
131
132	/*
133	 * Join the two strings together, ensuring that the right thing
134	 * happens if the last component is empty, or the dirname is root.
135	 */
136	if (resolved[0] == '/' && resolved[1] == '\0')
137		rootd = 1;
138	else
139		rootd = 0;
140
141	if (*wbuf) {
142		if (strlen(resolved) + strlen(wbuf) + rootd + 1 > PATH_MAX) {
143			errno = ENAMETOOLONG;
144			goto err1;
145		}
146		if (rootd == 0)
147			(void)strcat(resolved, "/");
148		(void)strcat(resolved, wbuf);
149	}
150
151	/* Go back to where we came from. */
152	if (fchdir(fd) < 0) {
153		serrno = errno;
154		goto err2;
155	}
156
157	/* It's okay if the close fails, what's an fd more or less? */
158	(void)_close(fd);
159	return (resolved);
160
161err1:	serrno = errno;
162	(void)fchdir(fd);
163err2:	(void)_close(fd);
164	errno = serrno;
165	return (NULL);
166}
167