stdlib/xpg_basename.c

   1 /* Return basename of given pathname according to the weird XPG specification.
   2    Copyright (C) 1997-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20 #include <libgen.h>
  21
  22
  23 char *
  24 __xpg_basename (char *filename)
  25 {
  26   char *p;
  27
  28   if (filename == NULL || filename[0] == '\0')
  29     /* We return a pointer to a static string containing ".".  */
  30     p = (char *) ".";
  31   else
  32     {
  33       p = strrchr (filename, '/');
  34
  35       if (p == NULL)
  36         /* There is no slash in the filename.  Return the whole string.  */
  37         p = filename;
  38       else
  39         {
  40           if (p[1] == '\0')
  41             {
  42               /* We must remove trailing '/'.  */
  43               while (p > filename && p[-1] == '/')
  44                 --p;
  45
  46               /* Now we can be in two situations:
  47                  a) the string only contains '/' characters, so we return
  48                     '/'
  49                  b) p points past the last component, but we have to remove
  50                     the trailing slash.  */
  51               if (p > filename)
  52                 {
  53                   *p-- = '\0';
  54                   while (p > filename && p[-1] != '/')
  55                     --p;
  56                 }
  57               else
  58                 /* The last slash we already found is the right position
  59                    to return.  */
  60                 while (p[1] != '\0')
  61                   ++p;
  62             }
  63           else
  64             /* Go to the first character of the name.  */
  65             ++p;
  66         }
  67     }
  68
  69   return p;
  70 }