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diff --git a/bin/ln/ln.c b/bin/ln/ln.c
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+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 1987, 1993, 1994
+ * The Regents of the University of California. All rights reserved.
+ *
+ * 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. 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.
+ */
+
+#include <sys/param.h>
+#include <sys/stat.h>
+
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static bool fflag; /* Unlink existing files. */
+static bool Fflag; /* Remove empty directories also. */
+static bool hflag; /* Check new name for symlink first. */
+static bool iflag; /* Interactive mode. */
+static bool Pflag; /* Create hard links to symlinks. */
+static bool sflag; /* Symbolic, not hard, link. */
+static bool vflag; /* Verbose output. */
+static bool wflag; /* Warn if symlink target does not
+ * exist, and -f is not enabled. */
+static char linkch;
+
+static int linkit(const char *, const char *, bool);
+static void link_usage(void) __dead2;
+static void usage(void) __dead2;
+
+int
+main(int argc, char *argv[])
+{
+ struct stat sb;
+ char *targetdir;
+ int ch, exitval;
+
+ /*
+ * Test for the special case where the utility is called as
+ * "link", for which the functionality provided is greatly
+ * simplified.
+ */
+ if (strcmp(getprogname(), "link") == 0) {
+ while (getopt(argc, argv, "") != -1)
+ link_usage();
+ argc -= optind;
+ argv += optind;
+ if (argc != 2)
+ link_usage();
+ if (lstat(argv[1], &sb) == 0)
+ errc(1, EEXIST, "%s", argv[1]);
+ /*
+ * We could simply call link(2) here, but linkit()
+ * performs additional checks and gives better
+ * diagnostics.
+ */
+ exit(linkit(argv[0], argv[1], false));
+ }
+
+ while ((ch = getopt(argc, argv, "FLPfhinsvw")) != -1)
+ switch (ch) {
+ case 'F':
+ Fflag = true;
+ break;
+ case 'L':
+ Pflag = false;
+ break;
+ case 'P':
+ Pflag = true;
+ break;
+ case 'f':
+ fflag = true;
+ iflag = false;
+ wflag = false;
+ break;
+ case 'h':
+ case 'n':
+ hflag = true;
+ break;
+ case 'i':
+ iflag = true;
+ fflag = false;
+ break;
+ case 's':
+ sflag = true;
+ break;
+ case 'v':
+ vflag = true;
+ break;
+ case 'w':
+ wflag = true;
+ break;
+ case '?':
+ default:
+ usage();
+ }
+
+ argv += optind;
+ argc -= optind;
+
+ linkch = sflag ? '-' : '=';
+ if (!sflag)
+ Fflag = false;
+ if (Fflag && !iflag) {
+ fflag = true;
+ wflag = false; /* Implied when fflag is true */
+ }
+
+ switch (argc) {
+ case 0:
+ usage();
+ /* NOTREACHED */
+ case 1: /* ln source */
+ exit(linkit(argv[0], ".", true));
+ case 2: /* ln source target */
+ exit(linkit(argv[0], argv[1], false));
+ default:
+ ;
+ }
+ /* ln source1 source2 directory */
+ targetdir = argv[argc - 1];
+ if (hflag && lstat(targetdir, &sb) == 0 && S_ISLNK(sb.st_mode)) {
+ /*
+ * We were asked not to follow symlinks, but found one at
+ * the target--simulate "not a directory" error
+ */
+ errno = ENOTDIR;
+ err(1, "%s", targetdir);
+ }
+ if (stat(targetdir, &sb))
+ err(1, "%s", targetdir);
+ if (!S_ISDIR(sb.st_mode))
+ usage();
+ for (exitval = 0; *argv != targetdir; ++argv)
+ exitval |= linkit(*argv, targetdir, true);
+ exit(exitval);
+}
+
+/*
+ * Two pathnames refer to the same directory entry if the directories match
+ * and the final components' names match.
+ */
+static int
+samedirent(const char *path1, const char *path2)
+{
+ const char *file1, *file2;
+ char pathbuf[PATH_MAX];
+ struct stat sb1, sb2;
+
+ if (strcmp(path1, path2) == 0)
+ return 1;
+ file1 = strrchr(path1, '/');
+ if (file1 != NULL)
+ file1++;
+ else
+ file1 = path1;
+ file2 = strrchr(path2, '/');
+ if (file2 != NULL)
+ file2++;
+ else
+ file2 = path2;
+ if (strcmp(file1, file2) != 0)
+ return 0;
+ if (file1 - path1 >= PATH_MAX || file2 - path2 >= PATH_MAX)
+ return 0;
+ if (file1 == path1)
+ memcpy(pathbuf, ".", 2);
+ else {
+ memcpy(pathbuf, path1, file1 - path1);
+ pathbuf[file1 - path1] = '\0';
+ }
+ if (stat(pathbuf, &sb1) != 0)
+ return 0;
+ if (file2 == path2)
+ memcpy(pathbuf, ".", 2);
+ else {
+ memcpy(pathbuf, path2, file2 - path2);
+ pathbuf[file2 - path2] = '\0';
+ }
+ if (stat(pathbuf, &sb2) != 0)
+ return 0;
+ return sb1.st_dev == sb2.st_dev && sb1.st_ino == sb2.st_ino;
+}
+
+/*
+ * Create a link to source. If target is a directory (and some additional
+ * conditions apply, see comments within) the link will be created within
+ * target and have the basename of source. Otherwise, the link will be
+ * named target. If isdir is true, target has already been determined to
+ * be a directory; otherwise, we will check, if needed.
+ */
+static int
+linkit(const char *source, const char *target, bool isdir)
+{
+ char path[PATH_MAX];
+ char wbuf[PATH_MAX];
+ char bbuf[PATH_MAX];
+ struct stat sb;
+ const char *p;
+ int ch, first;
+ bool append, exists;
+
+ if (!sflag) {
+ /* If source doesn't exist, quit now. */
+ if ((Pflag ? lstat : stat)(source, &sb)) {
+ warn("%s", source);
+ return (1);
+ }
+ /* Only symbolic links to directories. */
+ if (S_ISDIR(sb.st_mode)) {
+ errno = EISDIR;
+ warn("%s", source);
+ return (1);
+ }
+ }
+
+ /*
+ * Append a slash and the source's basename if:
+ * - the target is "." or ends in "/" or "/.", or
+ * - the target is a directory (and not a symlink if hflag) and
+ * Fflag is not set
+ */
+ if ((p = strrchr(target, '/')) == NULL)
+ p = target;
+ else
+ p++;
+ append = false;
+ if (p[0] == '\0' || (p[0] == '.' && p[1] == '\0')) {
+ append = true;
+ } else if (!Fflag) {
+ if (isdir || (lstat(target, &sb) == 0 && S_ISDIR(sb.st_mode)) ||
+ (!hflag && stat(target, &sb) == 0 && S_ISDIR(sb.st_mode))) {
+ append = true;
+ }
+ }
+ if (append) {
+ if (strlcpy(bbuf, source, sizeof(bbuf)) >= sizeof(bbuf) ||
+ (p = basename(bbuf)) == NULL /* can't happen */ ||
+ snprintf(path, sizeof(path), "%s/%s", target, p) >=
+ (ssize_t)sizeof(path)) {
+ errno = ENAMETOOLONG;
+ warn("%s", source);
+ return (1);
+ }
+ target = path;
+ }
+
+ /*
+ * If the link source doesn't exist, and a symbolic link was
+ * requested, and -w was specified, give a warning.
+ */
+ if (sflag && wflag) {
+ if (*source == '/') {
+ /* Absolute link source. */
+ if (stat(source, &sb) != 0)
+ warn("warning: %s inaccessible", source);
+ } else {
+ /*
+ * Relative symlink source. Try to construct the
+ * absolute path of the source, by appending `source'
+ * to the parent directory of the target.
+ */
+ strlcpy(bbuf, target, sizeof(bbuf));
+ p = dirname(bbuf);
+ if (p != NULL) {
+ (void)snprintf(wbuf, sizeof(wbuf), "%s/%s",
+ p, source);
+ if (stat(wbuf, &sb) != 0)
+ warn("warning: %s", source);
+ }
+ }
+ }
+
+ /*
+ * If the file exists, first check it is not the same directory entry.
+ */
+ exists = lstat(target, &sb) == 0;
+ if (exists) {
+ if (!sflag && samedirent(source, target)) {
+ warnx("%s and %s are the same directory entry",
+ source, target);
+ return (1);
+ }
+ }
+ /*
+ * Then unlink it forcibly if -f was specified
+ * and interactively if -i was specified.
+ */
+ if (fflag && exists) {
+ if (Fflag && S_ISDIR(sb.st_mode)) {
+ if (rmdir(target)) {
+ warn("%s", target);
+ return (1);
+ }
+ } else if (unlink(target)) {
+ warn("%s", target);
+ return (1);
+ }
+ } else if (iflag && exists) {
+ fflush(stdout);
+ fprintf(stderr, "replace %s? ", target);
+
+ first = ch = getchar();
+ while(ch != '\n' && ch != EOF)
+ ch = getchar();
+ if (first != 'y' && first != 'Y') {
+ fprintf(stderr, "not replaced\n");
+ return (1);
+ }
+
+ if (Fflag && S_ISDIR(sb.st_mode)) {
+ if (rmdir(target)) {
+ warn("%s", target);
+ return (1);
+ }
+ } else if (unlink(target)) {
+ warn("%s", target);
+ return (1);
+ }
+ }
+
+ /* Attempt the link. */
+ if (sflag ? symlink(source, target) :
+ linkat(AT_FDCWD, source, AT_FDCWD, target,
+ Pflag ? 0 : AT_SYMLINK_FOLLOW)) {
+ warn("%s", target);
+ return (1);
+ }
+ if (vflag)
+ (void)printf("%s %c> %s\n", target, linkch, source);
+ return (0);
+}
+
+static void
+link_usage(void)
+{
+ (void)fprintf(stderr, "usage: link source_file target_file\n");
+ exit(1);
+}
+
+static void
+usage(void)
+{
+ (void)fprintf(stderr, "%s\n%s\n",
+ "usage: ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file [target_file]",
+ " ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file ... target_dir");
+ exit(1);
+}
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