stdlib/xpg_basename.c

   1 /* Return basename of given pathname according to the weird XPG specification.
   2    Copyright (C) 1997-2019 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <string.h>
  21 #include <libgen.h>
  22
  23
  24 char *
  25 __xpg_basename (char *filename)
  26 {
  27   char *p;
  28
  29   if (filename == NULL || filename[0] == '\0')
  30     /* We return a pointer to a static string containing ".".  */
  31     p = (char *) ".";
  32   else
  33     {
  34       p = strrchr (filename, '/');
  35
  36       if (p == NULL)
  37         /* There is no slash in the filename.  Return the whole string.  */
  38         p = filename;
  39       else
  40         {
  41           if (p[1] == '\0')
  42             {
  43               /* We must remove trailing '/'.  */
  44               while (p > filename && p[-1] == '/')
  45                 --p;
  46
  47               /* Now we can be in two situations:
  48                  a) the string only contains '/' characters, so we return
  49                     '/'
  50                  b) p points past the last component, but we have to remove
  51                     the trailing slash.  */
  52               if (p > filename)
  53                 {
  54                   *p-- = '\0';
  55                   while (p > filename && p[-1] != '/')
  56                     --p;
  57                 }
  58               else
  59                 /* The last slash we already found is the right position
  60                    to return.  */
  61                 while (p[1] != '\0')
  62                   ++p;
  63             }
  64           else
  65             /* Go to the first character of the name.  */
  66             ++p;
  67         }
  68     }
  69
  70   return p;
  71 }