misc/dirname.c

   1 /* dirname - return directory part of PATH.
   2    Copyright (C) 1996, 2000, 2001, 2002 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <libgen.h>
  22 #include <string.h>
  23
  24
  25 char *
  26 dirname (char *path)
  27 {
  28   static const char dot[] = ".";
  29   char *last_slash;
  30
  31   /* Find last '/'.  */
  32   last_slash = path != NULL ? strrchr (path, '/') : NULL;
  33
  34   if (last_slash != NULL && last_slash != path && last_slash[1] == '\0')
  35     {
  36       /* Determine whether all remaining characters are slashes.  */
  37       char *runp;
  38
  39       for (runp = last_slash; runp != path; --runp)
  40         if (runp[-1] != '/')
  41           break;
  42
  43       /* The '/' is the last character, we have to look further.  */
  44       if (runp != path)
  45         last_slash = __memrchr (path, '/', runp - path);
  46     }
  47
  48   if (last_slash != NULL)
  49     {
  50       /* Determine whether all remaining characters are slashes.  */
  51       char *runp;
  52
  53       for (runp = last_slash; runp != path; --runp)
  54         if (runp[-1] != '/')
  55           break;
  56
  57       /* Terminate the path.  */
  58       if (runp == path)
  59         {
  60           /* The last slash is the first character in the string.  We have to
  61              return "/".  As a special case we have to return "//" if there
  62              are exactly two slashes at the beginning of the string.  See
  63              XBD 4.10 Path Name Resolution for more information.  */
  64           if (last_slash == path + 1)
  65             ++last_slash;
  66           else
  67             last_slash = path + 1;
  68         }
  69       else
  70         last_slash = runp;
  71
  72       last_slash[0] = '\0';
  73     }
  74   else
  75     /* This assignment is ill-designed but the XPG specs require to
  76        return a string containing "." in any case no directory part is
  77        found and so a static and constant string is required.  */
  78     path = (char *) dot;
  79
  80   return path;
  81 }