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., 9 Temple Place - Suite 330, Boston, MA 02111-1307,
  17    USA.
  18 */
  19
  20 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>,
  21    inspired by John P. Rouillard <rouilj@cs.umb.edu>.  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include <gnulib/config.h>
  25 #undef VERSION
  26 #undef PACKAGE_VERSION
  27 #undef PACKAGE_TARNAME
  28 #undef PACKAGE_STRING
  29 #undef PACKAGE
  30 #undef PACKAGE_NAME
  31 #include <config.h>
  32 #endif
  33
  34 #include <stdio.h>
  35 #if defined(HAVE_STRING_H) || defined(STDC_HEADERS)
  36 #include <string.h>
  37 #else
  38 #include <strings.h>
  39 #ifndef strchr
  40 #define strchr index
  41 #endif
  42 #endif
  43 #if defined(STDC_HEADERS)
  44 #include <stdlib.h>
  45 #endif
  46
  47 /* Return the next element of a colon-separated path.
  48    A null entry in the path is equivalent to "." (the current directory).
  49
  50    If NEW_PATH is non-NULL, set the path and return NULL.
  51    If NEW_PATH is NULL, return the next item in the string, or
  52    return NULL if there are no more elements.  */
  53
  54 char *
  55 next_element (new_path)
  56      char *new_path;
  57 {
  58   static char *path = NULL;     /* Freshly allocated copy of NEW_PATH.  */
  59   static char *end;             /* Start of next element to return.  */
  60   static int final_colon;       /* If zero, path didn't end with a colon.  */
  61   char *start;                  /* Start of path element to return.  */
  62
  63   if (new_path)
  64     {
  65       if (path)
  66         free (path);
  67       end = path = strdup (new_path);
  68       final_colon = 0;
  69       return NULL;
  70     }
  71
  72   if (*end == '\0')
  73     {
  74       if (final_colon)
  75         {
  76           final_colon = 0;
  77           return ".";
  78         }
  79       return NULL;
  80     }
  81
  82   start = end;
  83   final_colon = 1;              /* Maybe there will be one.  */
  84
  85   end = strchr (start, ':');
  86   if (end == start)
  87     {
  88       /* An empty path element.  */
  89       *end++ = '\0';
  90       return ".";
  91     }
  92   else if (end == NULL)
  93     {
  94       /* The last path element.  */
  95       end = strchr (start, '\0');
  96       final_colon = 0;
  97     }
  98   else
  99     *end++ = '\0';
 100
 101   return start;
 102 }
 103
 104 #ifdef TEST
 105 int
 106 main ()
 107 {
 108   char *p;
 109
 110   next_element (getenv ("PATH"));
 111   while (p = next_element (NULL))
 112     puts (p);
 113   exit (0);
 114 }
 115 #endif /* TEST */