From: Rob Biedenharn <rob@...>
Date: 2013-05-16T00:09:48+09:00
Subject: Re: Need help for Kernel methods


On 2013-May-15, at 10:27 , Love U Ruby wrote:

> Rob Biedenharn wrote in post #1108992:
> 
>>> what does it mean by `canonicalized absolute path`?
>>> 
>>> Why said `symlinks in the path is resolved`?
>> 
>> So that you don't have multiple aliases for a single file (as the
>> require is path sensetive).
>> 
>> -Rob
> 
> 
> @Rob - Could you give me a simple example to understand this method,if 
> possible?


I hope you think this is simple enough. The Kernel#_dir_ is essentially File.dirname(File.realpath(__FILE__)).

[ruby-2.0.0p0] code/ruby $ mkdir symlink
[ruby-2.0.0p0] code/ruby $ cd symlink
[ruby-2.0.0p0] ruby/symlink $ ls -al
total 0
drwxr-xr-x    2 rab  staff    68 May 15 11:00 .
drwxr-xr-x  171 rab  staff  5814 May 15 11:00 ..
[ruby-2.0.0p0] ruby/symlink $ mkdir -p real/path/to
[ruby-2.0.0p0] ruby/symlink $ touch real/path/to/file
[ruby-2.0.0p0] ruby/symlink $ ln -nsf real alt
[ruby-2.0.0p0] ruby/symlink $ ln -nsf real/path/to direct
[ruby-2.0.0p0] ruby/symlink $ ln -nsf alt/path/to indirect
[ruby-2.0.0p0] ruby/symlink $ ls -alR
total 24
drwxr-xr-x    6 rab  staff   204 May 15 11:02 .
drwxr-xr-x  171 rab  staff  5814 May 15 11:00 ..
lrwxr-xr-x    1 rab  staff     4 May 15 11:01 alt -> real
lrwxr-xr-x    1 rab  staff    12 May 15 11:02 direct -> real/path/to
lrwxr-xr-x    1 rab  staff    11 May 15 11:02 indirect -> alt/path/to
drwxr-xr-x    3 rab  staff   102 May 15 11:00 real

./real:
total 0
drwxr-xr-x  3 rab  staff  102 May 15 11:00 .
drwxr-xr-x  6 rab  staff  204 May 15 11:02 ..
drwxr-xr-x  3 rab  staff  102 May 15 11:00 path

./real/path:
total 0
drwxr-xr-x  3 rab  staff  102 May 15 11:00 .
drwxr-xr-x  3 rab  staff  102 May 15 11:00 ..
drwxr-xr-x  3 rab  staff  102 May 15 11:01 to

./real/path/to:
total 0
drwxr-xr-x  3 rab  staff  102 May 15 11:01 .
drwxr-xr-x  3 rab  staff  102 May 15 11:00 ..
-rw-r--r--  1 rab  staff    0 May 15 11:01 file
[ruby-2.0.0p0] ruby/symlink $ echo "Hi!" >> real/path/to/file 
-bash: !": event not found
[ruby-2.0.0p0] ruby/symlink $ echo "Hello" >> real/path/to/file 
[ruby-2.0.0p0] ruby/symlink $ cat alt/path/to/file
Hello
[ruby-2.0.0p0] ruby/symlink $ cat direct/file 
Hello
[ruby-2.0.0p0] ruby/symlink $ cat indirect/file 
Hello
[ruby-2.0.0p0] ruby/symlink $ echo ", World" >> real/path/to/file 
[ruby-2.0.0p0] ruby/symlink $ cat alt/path/to/file
Hello
, World
[ruby-2.0.0p0] ruby/symlink $ cat direct/file 
Hello
, World
[ruby-2.0.0p0] ruby/symlink $ cat indirect/file 
Hello
, World
[ruby-2.0.0p0] ruby/symlink $ irb
irb2.0.0> File.realpath('indirect/file')
#2.0.0 => "/Users/rab/code/ruby/symlink/real/path/to/file"
irb2.0.0> File.realpath('direct/file')
#2.0.0 => "/Users/rab/code/ruby/symlink/real/path/to/file"
irb2.0.0> File.realpath('alt/path/to/file')
#2.0.0 => "/Users/rab/code/ruby/symlink/real/path/to/file"

irb2.0.0> File.dirname(File.realpath('alt/path/to/file'))
#2.0.0 => "/Users/rab/code/ruby/symlink/real/path/to"

-Rob