/*	$NetBSD: execvp.c,v 1.2 1997/04/24 18:55:51 kleink Exp $	*/

/*-
 * Copyright (c) 1991, 1993
 *	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. 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)
#if 0
static char sccsid[] = "@(#)exec.c	8.1 (Berkeley) 6/4/93";
#else
static char rcsid[] = "$NetBSD: execvp.c,v 1.2 1997/04/24 18:55:51 kleink Exp $";
#endif
#endif /* LIBC_SCCS and not lint */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <unistd.h>
#include <paths.h>

extern char **environ;

int
execvp(name, argv)
	const char *name;
	char * const *argv;
{
	static int memsize;
	static char **memp;
	register int cnt, lp, ln;
	register char *p;
	int eacces = 0, etxtbsy = 0;
	char *bp, *cur, *path, buf[PATH_MAX];

	/* "" is not a valid filename; check this before traversing PATH. */
	if (name[0] == '\0') {
		errno = ENOENT;
		goto done;
	}
	/* If it's an absolute or relative path name, it's easy. */
	if (strchr(name, '/')) {
		bp = (char *)name;
		cur = path = NULL;
		goto retry;
	}
	bp = buf;

	/* Get the path we're searching. */
	if (!(path = getenv("PATH")))
		path = _PATH_DEFPATH;
	cur = path = strdup(path);

	while (p = strsep(&cur, ":")) {
		/*
		 * It's a SHELL path -- double, leading and trailing colons
		 * mean the current directory.
		 */
		if (!*p) {
			p = ".";
			lp = 1;
		} else
			lp = strlen(p);
		ln = strlen(name);

		/*
		 * If the path is too long complain.  This is a possible
		 * security issue; given a way to make the path too long
		 * the user may execute the wrong program.
		 */
		if (lp + ln + 2 > sizeof(buf)) {
			(void)write(STDERR_FILENO, "execvp: ", 8);
			(void)write(STDERR_FILENO, p, lp);
			(void)write(STDERR_FILENO, ": path too long\n", 16);
			continue;
		}
		bcopy(p, buf, lp);
		buf[lp] = '/';
		bcopy(name, buf + lp + 1, ln);
		buf[lp + ln + 1] = '\0';

retry:		(void)execve(bp, argv, environ);
		switch(errno) {
		case EACCES:
			eacces = 1;
			break;
		case ENOENT:
			break;
		case ENOEXEC:
			for (cnt = 0; argv[cnt]; ++cnt);
			if ((cnt + 2) * sizeof(char *) > memsize) {
				memsize = (cnt + 2) * sizeof(char *);
				if ((memp = realloc(memp, memsize)) == NULL) {
					memsize = 0;
					goto done;
				}
			}
			memp[0] = "sh";
			memp[1] = bp;
			bcopy(argv + 1, memp + 2, cnt * sizeof(char *));
			(void)execve(_PATH_BSHELL, memp, environ);
			goto done;
		case ETXTBSY:
			if (etxtbsy < 3)
				(void)sleep(++etxtbsy);
			goto retry;
		default:
			goto done;
		}
	}
	if (eacces)
		errno = EACCES;
	else if (!errno)
		errno = ENOENT;
done:	if (path)
		free(path);
	return (-1);
}