os: OpenFile creates incorrect file name on Windows

[epowsal]

windows os.OpenFile bug: if open path like this:X:/aa:393.txt the create filename will be "aa"
it should panic.
1.20.5

[qmuntal]

@golang/windows

[qmuntal]

Could you share a code sample that we can use to reproduce this issue? Thanks.

[mauri870]

I'm able to reproduce it using os.OpenFile:

package main

import (
        "log"
        "os"
)

func main() {
        f, err := os.OpenFile("C:/aa:393.txt", os.O_RDWR|os.O_CREATE, 0755)
        if err != nil {
                log.Fatal(err)
        }
        defer f.Close()
}

From the win docs:

Use any character in the current code page for a name, including Unicode characters and characters in the extended character set (128–255), except for the following:

    The following reserved characters:
        < (less than)
        > (greater than)
        : (colon)
        " (double quote)
        / (forward slash)
        \ (backslash)
        | (vertical bar or pipe)
        ? (question mark)
        * (asterisk)

Weirdly enough trying any of the other reserved characters result in a proper error:

open H:/aa*393.txt: The filename, directory name, or volume label syntax is incorrect.
open H:/aa>393.txt: The filename, directory name, or volume label syntax is incorrect.
open H:/aa"393.txt: The filename, directory name, or volume label syntax is incorrect.
open H:/aa?393.txt: The filename, directory name, or volume label syntax is incorrect.
open H:/aa|393.txt: The filename, directory name, or volume label syntax is incorrect.

I'll try to work on a fix.

[mauri870]

Seems like python also allows a : in a file path:

.\python.exe -c "open('C:/aa:393.txt', 'w').close()" # ok, results in a file named "aa"

.\python.exe -c "open('C:/aa?393.txt', 'w').close()" # bad
Traceback (most recent call last):
  File "<string>", line 1, in <module>
OSError: [Errno 22] Invalid argument: 'H:/aa?393.txt'  

[ianlancetaylor]

This kind of sounds like a Windows bug to me. Why does Windows not return an error if it can't create the file?

[seankhliao]

It appears : addresses NTFS ALternate Data Streams, taking the form filename:stream, with :$DATA being the default stream.
So it's probably not a bug?

[mauri870]

I think you are right @seankhliao, aparently that is a thing. tdil

[alexbrainman]

@mauri870

I'm able to reproduce it using os.OpenFile:

Why would you use : in file name on Windows? You are looking for trouble.

Alex

[mauri870]

@seankhliao I think we can close this issue. The problem seems to be the use of : in the file name, which is used by NTFS data streams, as mentioned by you in previous comments.