lib/nextelem.c

   1 /* Return the next element of a path.
   2    Copyright (C) 1992 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  17    USA.
  18 */
  19
  20 /* Written by David MacKenzie <djm@gnu.org>,
  21    inspired by John P. Rouillard <rouilj@cs.umb.edu>.  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include <config.h>
  25 #endif
  26
  27 #include <stdio.h>
  28 #if defined(HAVE_STRING_H) || defined(STDC_HEADERS)
  29 #include <string.h>
  30 #else
  31 #include <strings.h>
  32 #ifndef strchr
  33 #define strchr index
  34 #endif
  35 #endif
  36 #if defined(STDC_HEADERS)
  37 #include <stdlib.h>
  38 #endif
  39
  40 #include "nextelem.h"
  41
  42
  43 /* Return the next element of a colon-separated path.
  44    A null entry in the path is equivalent to "." (the current directory).
  45
  46    If NEW_PATH is non-NULL, set the path and return NULL.
  47    If NEW_PATH is NULL, return the next item in the string, or
  48    return NULL if there are no more elements.  */
  49
  50 char *
  51 next_element (const char *new_path, int curdir_ok)
  52 {
  53   static char *path = NULL;     /* Freshly allocated copy of NEW_PATH.  */
  54   static char *end;             /* Start of next element to return.  */
  55   static int final_colon;       /* If zero, path didn't end with a colon.  */
  56   char *start;                  /* Start of path element to return.  */
  57
  58   if (new_path)
  59     {
  60       if (path)
  61         free (path);
  62       end = path = strdup (new_path);
  63       final_colon = 0;
  64       return NULL;
  65     }
  66
  67   if (*end == '\0')
  68     {
  69       if (final_colon)
  70         {
  71           final_colon = 0;
  72           return curdir_ok ? "." : "";
  73         }
  74       return NULL;
  75     }
  76
  77   start = end;
  78   final_colon = 1;              /* Maybe there will be one.  */
  79
  80   end = strchr (start, ':');
  81   if (end == start)
  82     {
  83       /* An empty path element.  */
  84       *end++ = '\0';
  85       return curdir_ok ? "." : "";
  86     }
  87   else if (end == NULL)
  88     {
  89       /* The last path element.  */
  90       end = strchr (start, '\0');
  91       final_colon = 0;
  92     }
  93   else
  94     *end++ = '\0';
  95
  96   return start;
  97 }
  98
  99 #ifdef TEST
 100 int
 101 main ()
 102 {
 103   char *p;
 104
 105   next_element (getenv ("PATH"));
 106   while (p = next_element (NULL))
 107     puts (p);
 108   exit (0);
 109 }
 110 #endif /* TEST */