tools/relpath.c

   1 /*
   2  * Compute the relative path needed to go from one Unix dir to another
   3  *
   4  * Copyright 2006 Alexandre Julliard
   5  *
   6  * This 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  * This 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 this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  19  */
  20
  21 #include "config.h"
  22
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26
  27 /* determine where the destination path is located relative to the 'from' path */
  28 static const char *get_relative_path( const char *from, const char *dest, unsigned int *dotdots )
  29 {
  30 #define DIR_END(p)  (*(p) == 0 || *(p) == '/')
  31     const char *start;
  32
  33     /* a path of "." is equivalent to an empty path */
  34     if (!strcmp( from, "." )) from = "";
  35
  36     *dotdots = 0;
  37     for (;;)
  38     {
  39         while (*from == '/') from++;
  40         while (*dest == '/') dest++;
  41         start = dest;  /* save start of next path element */
  42         if (!*from) break;
  43
  44         while (!DIR_END(from) && *from == *dest) { from++; dest++; }
  45         if (DIR_END(from) && DIR_END(dest)) continue;
  46
  47         /* count remaining elements in 'from' */
  48         do
  49         {
  50             (*dotdots)++;
  51             while (!DIR_END(from)) from++;
  52             while (*from == '/') from++;
  53         }
  54         while (*from);
  55         break;
  56     }
  57     return start;
  58 #undef DIR_END
  59 }
  60
  61
  62 int main( int argc, char *argv[] )
  63 {
  64     const char *start;
  65     unsigned int dotdots = 0;
  66
  67     if (argc != 3)
  68     {
  69         fprintf( stderr, "Usage: %s fromdir todir\n", argv[0] );
  70         exit(1);
  71     }
  72     start = get_relative_path( argv[1], argv[2], &dotdots );
  73
  74     if (!start[0] && !dotdots) printf( ".\n" );
  75     else
  76     {
  77         while (dotdots)
  78         {
  79             printf( ".." );
  80             dotdots--;
  81             if (dotdots || start[0]) printf( "/" );
  82         }
  83         printf( "%s\n", start );
  84     }
  85     exit(0);
  86 }