/**
 * Copyright (c) 2000 Dan Papasian.  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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 * $FreeBSD: src/usr.bin/which/which.c,v 1.5 2002/06/30 06:02:39 tjr Exp $");
 * $DragonFly: src/usr.bin/which/which.c,v 1.3 2005/08/30 22:42:15 liamfoy Exp $
 */

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

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

static void     usage(void);
static int      print_matches(char *, char *);

int    silent;
int    allpaths;

int
main(int argc, char **argv)
{
       char *p, *path;
       ssize_t pathlen;
       int opt, status;

       status = EXIT_SUCCESS;

       while ((opt = getopt(argc, argv, "as")) != -1) {
               switch (opt) {
               case 'a':
                       allpaths = 1;
                       break;
               case 's':
                       silent = 1;
                       break;
               default:
                       usage();
                       break;
               }
       }

       argv += optind;
       argc -= optind;

       if (argc == 0)
             usage();
        
       if ((p = getenv("PATH")) == NULL)
               exit(EXIT_FAILURE);
       pathlen = strlen(p) + 1;
       path = malloc(pathlen);
       if (path == NULL)
               err(EXIT_FAILURE, "malloc failed");

       while (argc > 0) {
               memcpy(path, p, pathlen);

               if (strlen(*argv) >= FILENAME_MAX ||
                   print_matches(path, *argv) == -1)
                       status = EXIT_FAILURE;

               argv++;
               argc--;
       }

       exit(status);
}

static void
usage(void)
{
       fprintf(stderr, "usage: which [-as] program ...\n");
       exit(EXIT_FAILURE);
}

static int
is_there(const char *candidate)
{
       struct stat fin;

       /* XXX work around access(2) false positives for superuser */
       if (access(candidate, X_OK) == 0 &&
           stat(candidate, &fin) == 0 &&
           S_ISREG(fin.st_mode) &&
           (getuid() != 0 ||
           (fin.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) != 0)) {
               if (!silent)
                       printf("%s\n", candidate);
               return (1);
       }
       return (0);
}

static int
print_matches(char *path, char *filename)
{
       char candidate[PATH_MAX];
       const char *d;
       int found;

       if (strchr(filename, '/') != NULL)
               return (is_there(filename) ? 0 : -1);
       found = 0;
       while ((d = strsep(&path, ":")) != NULL) {
               if (*d == '\0')
                       d = ".";
               if (snprintf(candidate, sizeof(candidate), "%s/%s", d,
                   filename) >= (int)sizeof(candidate))
                       continue;
               if (is_there(candidate)) {
                       found = 1;
                       if (!allpaths)
                               break;
               }
       }
       return (found ? 0 : -1);
}