/*      $OpenBSD: ln.c,v 1.25 2019/06/28 13:34:59 deraadt Exp $ */
/*      $NetBSD: ln.c,v 1.10 1995/03/21 09:06:10 cgd Exp $      */

/*
 * 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/types.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>

int     fflag;                          /* Unlink existing files. */
int     hflag;                          /* Check new name for symlink first. */
int     Pflag;                          /* Hard link to symlink. */
int     sflag;                          /* Symbolic, not hard, link. */

int     linkit(char *, char *, int);
void    usage(void) __dead;

int
main(int argc, char *argv[])
{
        struct stat sb;
        int ch, exitval;
        char *sourcedir;

        if (pledge("stdio rpath cpath", NULL) == -1)
                err(1, "pledge");

        while ((ch = getopt(argc, argv, "fhLnPs")) != -1)
                switch (ch) {
                case 'f':
                        fflag = 1;
                        break;
                case 'h':
                case 'n':
                        hflag = 1;
                        break;
                case 'L':
                        Pflag = 0;
                        break;
                case 'P':
                        Pflag = 1;
                        break;
                case 's':
                        sflag = 1;
                        break;
                default:
                        usage();
                }

        argv += optind;
        argc -= optind;

        switch(argc) {
        case 0:
                usage();
        case 1:                         /* ln target */
                exit(linkit(argv[0], ".", 1));
        case 2:                         /* ln target source */
                exit(linkit(argv[0], argv[1], 0));
        }
                                        /* ln target1 target2 directory */
        sourcedir = argv[argc - 1];
        if (stat(sourcedir, &sb))
                err(1, "%s", sourcedir);
        if (!S_ISDIR(sb.st_mode))
                usage();
        for (exitval = 0; *argv != sourcedir; ++argv)
                exitval |= linkit(*argv, sourcedir, 1);
        exit(exitval);
}

 /*
  * Nomenclature warning!
  *
  * In this source "target" and "source" are used the opposite way they
  * are used in the ln(1) manual.  Here "target" is the existing file and
  * "source" specifies the to-be-created link to "target".
  */
int
linkit(char *target, char *source, int isdir)
{
        struct stat sb;
        char *p, path[PATH_MAX];
        int (*statf)(const char *, struct stat *);
        int exists, n;

        if (!sflag) {
                /* If target doesn't exist, quit now. */
                if ((Pflag ? lstat : stat)(target, &sb)) {
                        warn("%s", target);
                        return (1);
                }
                /* Only symbolic links to directories. */
                if (S_ISDIR(sb.st_mode)) {
                        warnc(EISDIR, "%s", target);
                        return (1);
                }
        }

        statf = hflag ? lstat : stat;

        /* If the source is a directory, append the target's name. */
        if (isdir || (!statf(source, &sb) && S_ISDIR(sb.st_mode))) {
                if ((p = basename(target)) == NULL) {
                        warn("%s", target);
                        return (1);
                }
                n = snprintf(path, sizeof(path), "%s/%s", source, p);
                if (n < 0 || n >= sizeof(path)) {
                        warnc(ENAMETOOLONG, "%s/%s", source, p);
                        return (1);
                }
                source = path;
        }

        exists = (lstat(source, &sb) == 0);
        /*
         * If doing hard links and the source (destination) exists and it
         * actually is the same file like the target (existing file), we
         * complain that the files are identical.  If -f is specified, we
         * accept the job as already done and return with success.
         */
        if (exists && !sflag) {
                struct stat tsb;

                if ((Pflag ? lstat : stat)(target, &tsb)) {
                        warn("%s: disappeared", target);
                        return (1);
                }

                if (tsb.st_dev == sb.st_dev && tsb.st_ino == sb.st_ino) {
                        if (fflag)
                                return (0);
                        else {
                                warnx("%s and %s are identical (nothing done).",
                                    target, source);
                                return (1);
                        }
                }
        }
        /*
         * If the file exists, and -f was specified, unlink it.
         * Attempt the link.
         */
        if ((fflag && unlink(source) == -1 && errno != ENOENT) ||
            (sflag ? symlink(target, source) :
            linkat(AT_FDCWD, target, AT_FDCWD, source,
            Pflag ? 0 : AT_SYMLINK_FOLLOW))) {
                warn("%s", source);
                return (1);
        }

        return (0);
}

void
usage(void)
{
        extern char *__progname;

        (void)fprintf(stderr,
            "usage: %s [-fhLnPs] source [target]\n"
            "       %s [-fLPs] source ... [directory]\n",
            __progname, __progname);
        exit(1);
}