On Fri, 31 Jan 1997, Chris G. Demetriou wrote:
 > use of 'which' is a fatal flaw in this patch.

Todd Vierling writes:
 > Funny; I don't see why.  If you're worried about security, that's one thing
 > (a root user should know his $PATH--this isn't setuid); if you're worried
 > about compatibility, there should be no problem using which.  The binary
 > /usr/bin/which (which sh uses, instead of csh's builtin) works as this
 > script uses it; if it finds cc/gcc, it prints only the first instance, and
 > if it doesn't, it prints nothing. 

On Sat, 1 Feb 1997, Christos Zoulas wrote:
 > Which is a nasty csh program. It sources your .cshrc with $prompt defined,
 > and checks each component of the path and aliases for the word(s) you pass
 > it. If you are not using csh this is losing.
 > 
 > A better fix is to add a whence builtin in the Bourne shell, but I still
 > don't like this much.

Argh - I had hoped we would long ago have replaced that very nasty
hack.  Even when I was a die-hard csh user I found the csh-script "which"
to be extremely unhelpful and wrong.  And now csh actually has a built-in
which, so the script should at least be:
	#!/bin/csh -f
	which $*
Actually, since this came up, I found a strong urge to write a sane C
version of "which"; appended.  Comments are welcome;  send-pr will
follow later.  If this goes in the original patch from der Mouse should
be OK too :-)

  -  Arne H. J.

/*	$NetBSD$	*/

/*-
 * Copyright (c) 1996 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Arne H. Juul.
 *
 * 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 NetBSD 
 *	  Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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.
 */

#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1997\n\
	The NetBSD Foundation.  All rights reserved.\n";

static char rcsid[] = "$NetBSD$";
#endif /* not lint */

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

#include <locale.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void usage();
/*
 * which --
 *	This which is different from historic which.  But then historic
 *	which never was sane, even for csh users.
 */
int
main(argc, argv)
	int argc;
	char *argv[];
{
	unsigned int len, maxlen, comlen, tplen;
	struct stat s;
	char *path, *p, *try, *trypath, *command;

	setlocale(LC_ALL, "");

	if (argc != 2) usage();

	setuid(geteuid()); /* for sanity of access(2) */
	command = argv[1];
	comlen = strlen(command);
	if (strchr(command, '/')) {
		if ((stat(command, &s) == 0) &&
		    S_ISREG(s.st_mode) && !access(command, X_OK)) {
			printf("%s\n", command);
			exit(0);
		} else {
			fprintf(stderr, "%s not found\n", command);
			exit(1);
		}
	}
	path = getenv("PATH");
	if (!path) {
		fprintf(stderr, "which: no PATH in environment\n");
		exit(1);
	}
	p = strdup(path);
	maxlen = 0;
	try = NULL;
	while (p) {
		trypath = p;
		p = strchr(p, ':');
		if (p)
			*p++ = '\0' ;
		if (!*trypath)
			trypath = ".";
		tplen = strlen(trypath);
		len = tplen + 1 + comlen + 1;
		if (len > maxlen) {
			maxlen = len;
			try = realloc(try, maxlen);
			if (!try)
				err(1, "malloc");
		}
		strcpy(try, trypath);
		try[tplen] = '/';
		strcpy(try+tplen+1, command);
		if ((stat(try, &s) == 0) &&
		    S_ISREG(s.st_mode) && !access(try, X_OK)) {
			printf("%s\n", try);
			exit(0);
		}
	}
	fprintf(stderr, "no %s in path\n", command);
	exit(1);
	/* NOTREACHED */
}

static void
usage()
{
	fprintf(stderr, "usage: which command\n");
	exit(1);
}