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Olivier Certner
72bb9eb7b6
In getcwd_logical(), test for a '.' or '..' component in one of the most
straightforward and intelligible ways possible.
In particular, this removes a superfluous re-test of the the component's
first character being '.' when the first one did not pass and, more
importantly, prevents the second test from relying on a side-effect in
the first.
While here, for better clarity, replace the loop that searches for '/'
with a simple call to strchrnul().
Add high-level comments about what is going on.
While here, test explicitly that pointed 'char' values are not 0 ('\0')
(style(9)).
While here, separate the successive steps of getcwd_logical() with blank
lines.
No functional change (intended).
Discussed with: emaste
Fixes: 2df923c5d2 ("pwd: Clean up and adopt POSIX semantics")
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D59709
126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1991, 1993, 1994
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* The Regents of the University of California. All rights reserved.
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* Copyright (c) 2026 Dag-Erling Smørgrav
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <assert.h>
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#include <err.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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static char *
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getcwd_logical(void)
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{
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struct stat log, phy;
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char *pwd, *s, *e;
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/* $PWD is set and absolute */
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if ((pwd = getenv("PWD")) == NULL || *pwd != '/')
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return (NULL);
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/* $PWD does not contain /./ or /../ */
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e = pwd;
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do {
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assert(*e == '/');
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s = e + 1; /* Beginning of next component (may point to NUL). */
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/* Search for the component's end. */
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e = strchrnul(s, '/');
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if (s[0] == '.' && (s + 1 == e || (s[1] == '.' && s + 2 == e)))
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return (NULL);
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} while (*e != '\0');
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/* $PWD refers to the current directory */
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if (stat(pwd, &log) != 0 || stat(".", &phy) != 0 ||
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log.st_dev != phy.st_dev || log.st_ino != phy.st_ino)
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return (NULL);
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return (pwd);
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}
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static char *
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getcwd_physical(void)
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{
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static char pwd[MAXPATHLEN];
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return (getcwd(pwd, sizeof(pwd)));
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}
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static void
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usage(void)
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{
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(void)fprintf(stderr, "usage: pwd [-L | -P]\n");
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exit(1);
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}
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int
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main(int argc, char *argv[])
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{
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char *pwd;
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int opt;
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bool logical;
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logical = true;
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while ((opt = getopt(argc, argv, "LP")) != -1) {
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switch (opt) {
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case 'L':
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logical = true;
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break;
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case 'P':
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logical = false;
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break;
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default:
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usage();
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}
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}
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argc -= optind;
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argv += optind;
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if (argc != 0)
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usage();
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/*
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* If we're trying to find the logical current directory and that
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* fails, behave as if -P was specified.
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*/
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if ((logical && (pwd = getcwd_logical()) != NULL) ||
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(pwd = getcwd_physical()) != NULL)
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printf("%s\n", pwd);
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else
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err(1, ".");
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if (fflush(stdout) != 0)
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err(1, "stdout");
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exit(0);
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}
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