lib/nextelem.c

   1 /* Return the next element of a path.
   2    Copyright (C) 1992,2005 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 #include <config.h>
  24
  25
  26 #include <stdio.h>
  27 #if defined HAVE_STRING_H || defined STDC_HEADERS
  28 #include <string.h>
  29 #else
  30 #include <strings.h>
  31 #ifndef strchr
  32 #define strchr index
  33 #endif
  34 #endif
  35 #if defined STDC_HEADERS
  36 #include <stdlib.h>
  37 #endif
  38
  39 #include "nextelem.h"
  40
  41
  42 /* Return the next element of a colon-separated path.
  43    A null entry in the path is equivalent to "." (the current directory).
  44
  45    If NEW_PATH is non-NULL, set the path and return NULL.
  46    If NEW_PATH is NULL, return the next item in the string, or
  47    return NULL if there are no more elements.  */
  48
  49 char *
  50 next_element (const char *new_path, int curdir_ok)
  51 {
  52   static char *path = NULL;     /* Freshly allocated copy of NEW_PATH.  */
  53   static char *end;             /* Start of next element to return.  */
  54   static int final_colon;       /* If zero, path didn't end with a colon.  */
  55   char *start;                  /* Start of path element to return.  */
  56
  57   if (new_path)
  58     {
  59       if (path)
  60         free (path);
  61       end = path = strdup (new_path);
  62       final_colon = 0;
  63       return NULL;
  64     }
  65
  66   if (*end == '\0')
  67     {
  68       if (final_colon)
  69         {
  70           final_colon = 0;
  71           return curdir_ok ? "." : "";
  72         }
  73       return NULL;
  74     }
  75
  76   start = end;
  77   final_colon = 1;              /* Maybe there will be one.  */
  78
  79   end = strchr (start, ':');
  80   if (end == start)
  81     {
  82       /* An empty path element.  */
  83       *end++ = '\0';
  84       return curdir_ok ? "." : "";
  85     }
  86   else if (end == NULL)
  87     {
  88       /* The last path element.  */
  89       end = strchr (start, '\0');
  90       final_colon = 0;
  91     }
  92   else
  93     *end++ = '\0';
  94
  95   return start;
  96 }
  97
  98 #ifdef TEST
  99 int
 100 main ()
 101 {
 102   char *p;
 103
 104   next_element (getenv ("PATH"));
 105   while (p = next_element (NULL))
 106     puts (p);
 107   exit (0);
 108 }
 109 #endif /* TEST */