Strange behaviors of fs.readdir(dir) and process.chdir(dir) on Windows when 'dir' is a dive letter

[duanyao]

My test code for fs.readdir:

d:\project\MyNodeJS\dir.js:

var fs = require('fs');
var dir = process.argv[2];
fs.readdir(dir, function(error, files) {
    if (error) {
      console.log(error);
      return;
    }
    for (var i = 0; i < files.length; ++i) {
      console.log(files[i]);
    }
});

Run the code (suppose the current directory is C:\Users\Administrator):

C:\Users\Administrator>cd /d d:\
d:\>node d:\project\MyNodeJS\dir.js c:

The output is the file list of current directory on drive c:(C:\Users\Administrator).

I think fs.readdir() should throw an error here because "c:" is not a directory.

My test code for process.chdir:
d:\project\MyNodeJS\cd.js:

var dir = process.argv[2];
process.chdir(dir);
console.log("current dir: " + process.cwd());

Run the code:

C:\Users\Administrator>cd /d d:\
d:\>node d:\project\MyNodeJS\cd.js c:

Output:

current dir: C:\Users\Administrator

I think process.chdir() should also throw an error here because "c:" is not a directory.

I also notice that Windows command 'dir' and 'cd' have samilar behaviors as dir.js and cd.js, treating a dive letter as the current directory on that drive. These behaviors are not documented, so I don't know whether they are features or bugs.

I tested node 0.8.18 on Windows 7 32bits system.

[bnoordhuis]

/cc @piscisaureus

[duanyao]

I have found an explanation on current directory on Windows:

http://blogs.msdn.com/b/oldnewthing/archive/2010/10/12/10073890.aspx
Why does each drive have its own current directory?

"Remembering the current directory for each drive has been preserved ever since, at least for batch files, although there isn't actually such a concept as a per-drive current directory in Win32. In Win32, all you have is a current directory. The appearance that each drive has its own current directory is a fake-out by cmd.exe, which uses strange environment variables to create the illusion to batch files that each drive has its own current directory."

So I think node.js don't have to follow cmd.exe's way.

[piscisaureus]

I disagree. We follow the path semantics of windows instead of inventing our own. The oldnewthing blog post you mention is mostly accurate except for the fact that drive-local directories is not limited to cmd.exe - the logic to interpret these is actually part of the win32 layer.

Also, other languages do the same, e.g. try this in python:

C:\Users\Bert Belder>d:

D:\>python
Python 2.7.2 (default, Jun 12 2011, 15:08:59) [MSC v.1500 32 bit (Intel)] on win
32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.chdir('c:')
>>> os.getcwd()
'C:\\Users\\Bert Belder'
>>>

You should note that process.chdir does actually change the current drive, so it behaves as cd /d which seems reasonable (and here we follow python, php, and the default behaviour of the c runtime.)

So this is working as intended.

[duanyao]

You are right, I read the MSDN aout "Naming Files, Paths, and Namespaces":
http://msdn.microsoft.com/zh-cn/library/windows/desktop/aa365247%28v=vs.85%29.aspx

If a file name begins with only a disk designator but not the backslash after the colon, it is interpreted as a relative path to the current directory on the drive with the specified letter. Note that the current directory may or may not be the root directory depending on what it was set to during the most recent "change directory" operation on that disk. Examples of this format are as follows:

• "C:tmp.txt" refers to a file named "tmp.txt" in the current directory on drive C.
• "C:tempdir\tmp.txt" refers to a file in a subdirectory to the current directory on drive C.

Win32 API SetCurrentDirectory() follows this description.