* SPDX-License-Identifier: BSD-3-Clause

/* $NetBSD: realpath.c,v 1.3 2023/05/25 17:24:17 kre Exp $ */
/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1991, 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/cdefs.h>
#if !defined(lint)
#if 0
__FBSDID("$FreeBSD: head/bin/realpath/realpath.c 326025 2017-11-20 19:49:47Z pfg $");
#else
__RCSID("$NetBSD: realpath.c,v 1.3 2023/05/25 17:24:17 kre Exp $");
#endif
#endif /* not lint */

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

#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static bool process(char *path);
static void usage(void) __dead;

static const char options[] = "Eeq";

char dot[] = ".";

bool eflag = false; /* default to -E mode */
bool qflag = false;

int
main(int argc, char *argv[])
{
char *path;
int ch, rval;

setprogname(argv[0]);

while ((ch = getopt(argc, argv, options)) != -1) {
switch (ch) {
case 'e':
eflag = true;
break;
case 'E':
eflag = false;
break;
case 'q':
qflag = true;
break;
case '?':
default:
usage();
}
}
argc -= optind;
argv += optind;

path = *argv != NULL ? *argv++ : dot;
rval = 0;
do {
if (path[0] == '\0') {
/* ignore -q for this one */
warnx("Invalid path ''");
rval = 1;
continue;
}
if (!process(path))
rval = 1;;
} while ((path = *argv++) != NULL);
exit(rval);
}

static bool
process(char *path)
{
char buf[PATH_MAX];
char buf2[sizeof buf];
char lbuf[PATH_MAX];
char *pp, *p, *q, *r, *s;
struct stat sb;
bool dir_reqd = false;

if ((p = realpath(path, buf)) != NULL) {
(void)printf("%s\n", p);
return true;
}

if (eflag || errno != ENOENT) {
if (!qflag)
warn("%s", path);
return false;
}

p = strrchr(path, '/');
while (p != NULL && p > &path[1] && p[1] == '\0') {
dir_reqd = true;
*p = '\0';
p = strrchr(path, '/');
}

if (p == NULL) {
p = realpath(".", buf);
if (p == NULL) {
warnx("relative path; current location unknown");
return false;
}
if ((size_t)snprintf(buf2, sizeof buf2, "%s/%s", buf, path)
>= sizeof buf2) {
if (!qflag)
warnx("%s/%s: path too long", p, path);
return false;
}
path = buf2;
p = strrchr(path, '/');
if (p == NULL)
abort();
}

*p = '\0';
pp = ++p;

q = path; r = buf; s = buf2;
while (realpath(*q ? q : "/", r) != NULL) {
ssize_t llen;

if (strcmp(r, "/") == 0 || strcmp(r, "//") == 0)
r++;
if ((size_t)snprintf(s, sizeof buf, "%s/%s", r, pp)
>= sizeof buf)
return false;

if (lstat(s, &sb) == -1 || !S_ISLNK(sb.st_mode)) {
(void)printf("%s\n", s);
return true;
}

q = strchr(r, '\0');
if (q >= &r[sizeof buf - 3]) {
*p = '/';
if (!qflag)
warnx("Expanded path for %s too long\n", path);
return false;
}

if ((llen = readlink(s, lbuf, sizeof lbuf - 2)) == -1) {
*p = '/';
if (!qflag)
warn("%s", path);
return false;
}
lbuf[llen] = '\0';

if (lbuf[0] == '/') {
q = lbuf;
if (dir_reqd) {
lbuf[llen++] = '/';
lbuf[llen] = '\0';
}
} else {
if (q != buf2) {
q = buf2;
r = buf;
} else {
q = buf;
r = buf2;
}

if ((size_t)snprintf(q, sizeof buf, "%s/%s%s", r, lbuf,
(dir_reqd ? "/" : "")) >= sizeof buf) {
*p = '/';
if (!qflag)
warnx("Expanded path for %s too long\n",
path);
return false;
}
}

s = realpath(q, r);
if (s != NULL) {
/* this case should almost never happen (race) */
(void)printf("%s\n", s);
return true;
}
if (errno != ENOENT) {
*p = '/';
if (!qflag)
warn("%s", path);
return false;
}

pp = strrchr(q, '/');
if (pp == NULL) {
/* we just put one there, where did it go? */
abort();
}
if (dir_reqd) {
*pp = '\0';
pp = strrchr(q, '/');
if (pp == NULL)
abort();
}
*pp++ = '\0';

s = q;
}

*p = '/';

if (!qflag)
warn("%s", path);
return false;
}

static void
usage(void)
{

(void)fprintf(stderr, "usage: %s [-%s] [path ...]\n",
getprogname(), options);
exit(1);
}