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os.Chmod file.Chmod different behavior on Windows #39606

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TACIXAT opened this issue Jun 16, 2020 · 3 comments
Closed

os.Chmod file.Chmod different behavior on Windows #39606

TACIXAT opened this issue Jun 16, 2020 · 3 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. OS-Windows
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Backlog

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@TACIXAT
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TACIXAT commented Jun 16, 2020

What version of Go are you using (go version)?

$ go version
go version go1.14.2 windows/amd64

Does this issue reproduce with the latest release?

Didn't try.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
set GOHOSTARCH=amd64
set GOHOSTOS=windows

What did you do?

It does not work with file.Chmod().

	f, err := os.Open(path)
	if err != nil {
		return err
	}
	defer f.Close()

	fi, err := f.Stat()
	if err != nil {
		return err
	}

	m := fi.Mode()

	err = f.Chmod(m | 0222)
	if err != nil {
		return err
	}

What did you expect to see?

Success.

What did you see instead?

chmod C:\Users\me\prog\proj\file.txt: not supported by windows

It does work with os.Chmod().

	f, err := os.Open(path)
	if err != nil {
		return err
	}
	defer f.Close()

	fi, err := f.Stat()
	if err != nil {
		return err
	}

	m := fi.Mode()

	err = os.Chmod(path, m | 0222)
	if err != nil {
		return err
	}

I am sure there is some technical explanation for this, but from an API perspective it is a bit annoying.
@bcmills
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bcmills commented Jun 17, 2020

CC @alexbrainman @mattn

Could this be due to other stray bits in m? (What happens if you use (m&os.ModePerm)|0222 instead?

@bcmills bcmills added NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. OS-Windows labels Jun 17, 2020
@bcmills bcmills added this to the Backlog milestone Jun 17, 2020
@alexbrainman
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I briefly looked at this, and it appears that syscall.Fchmod is not implemented, while syscall.Chmod is. I don't remember why it happened this way.

I also noticed that os.TestChmod is skipped on windows. os.TestChmod actually checks that os.File.Chmod works. So, I would start by making os.TestChmod run on windows, and see where it gets you.

I don't see problem implementing syscall.Fchmod, given that we already have syscall.Chmod implementation.

Alex

@gopherbot
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Change https://golang.org/cl/250077 mentions this issue: os: implement File.Chmod on Windows

@golang golang locked and limited conversation to collaborators Sep 11, 2021
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