BSD 4_4_Lite1 release

[unix-history] / usr / src / lib / libc / stdlib / realpath.c

/*
* Copyright (c) 1994
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jan-Simon Pendry.
*
* 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.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)realpath.c  8.1 (Berkeley) 2/16/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/stat.h>

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
* char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
*
* Find the real name of path, by removing all ".", ".." and symlink
* components.  Returns (resolved) on success, or (NULL) on failure,
* in which case the path which caused trouble is left in (resolved).
*/
char *
realpath(path, resolved)
       const char *path;
       char *resolved;
{
       struct stat sb;
       int fd, n, rootd, serrno;
       char *p, *q, wbuf[MAXPATHLEN];

       /* Save the starting point. */
       if ((fd = open(".", O_RDONLY)) < 0) {
               (void)strcpy(resolved, ".");
               return (NULL);
       }

       /*
        * Find the dirname and basename from the path to be resolved.
        * Change directory to the dirname component.
        * lstat the basename part.
        *     if it is a symlink, read in the value and loop.
        *     if it is a directory, then change to that directory.
        * get the current directory name and append the basename.
        */
       (void)strncpy(resolved, path, MAXPATHLEN - 1);
       resolved[MAXPATHLEN - 1] = '\0';
loop:
       q = strrchr(resolved, '/');
       if (q != NULL) {
               p = q + 1;
               if (q == resolved)
                       q = "/";
               else {
                       do {
                               --q;
                       } while (q > resolved && *q == '/');
                       q[1] = '\0';
                       q = resolved;
               }
               if (chdir(q) < 0)
                       goto err1;
       } else
               p = resolved;

       /* Deal with the last component. */
       if (lstat(p, &sb) == 0) {
               if (S_ISLNK(sb.st_mode)) {
                       n = readlink(p, resolved, MAXPATHLEN);
                       if (n < 0)
                               goto err1;
                       resolved[n] = '\0';
                       goto loop;
               }
               if (S_ISDIR(sb.st_mode)) {
                       if (chdir(p) < 0)
                               goto err1;
                       p = "";
               }
       }

       /*
        * Save the last component name and get the full pathname of
        * the current directory.
        */
       (void)strcpy(wbuf, p);
       if (getcwd(resolved, MAXPATHLEN) == 0)
               goto err1;

       /*
        * Join the two strings together, ensuring that the right thing
        * happens if the last component is empty, or the dirname is root.
        */
       if (resolved[0] == '/' && resolved[1] == '\0')
               rootd = 1;
       else
               rootd = 0;

       if (*wbuf) {
               if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
                       errno = ENAMETOOLONG;
                       goto err1;
               }
               if (rootd == 0)
                       (void)strcat(resolved, "/");
               (void)strcat(resolved, wbuf);
       }

       /* Go back to where we came from. */
       if (fchdir(fd) < 0) {
               serrno = errno;
               goto err2;
       }

       /* It's okay if the close fails, what's an fd more or less? */
       (void)close(fd);
       return (resolved);

err1:   serrno = errno;
       (void)fchdir(fd);
err2:   (void)close(fd);
       errno = serrno;
       return (NULL);
}