doc: document opening hidden files on Windows by bzoz · Pull Request #15409 · nodejs/node

bzoz · 2017-09-14T13:03:18Z

Fixes: #14553

Checklist

documentation is changed or added
commit message follows commit guidelines

Affected core subsystem(s)

doc

Fixes: nodejs#14553

vsemozhetbyt · 2017-09-14T15:28:40Z

doc/api/fs.md

 [this MSDN page][MSDN-Rel-Path].

+*Note:* On Windows opening existing hidden file using the `w` flag (either
+through `fs.open` or `fs.writeFile`) will fail with `EPERM`. You can work


A nit: fs.open(), fs.writeFile() and fs.ftruncate()?

Should be either opening an existing hidden file or opening existing hidden files.

Please avoid the use of informal pronouns like you in the docs

seishun · 2017-09-14T16:22:27Z

doc/api/fs.md

+*Note:* On Windows opening existing hidden file using the `w` flag (either
+through `fs.open` or `fs.writeFile`) will fail with `EPERM`. You can work
+around this by opening the file with the `a` flag and then using `fs.ftruncate`
+to clear the file contents. 


Does ftruncate rewind the current file position to the beginning?

jasnell · 2017-09-14T18:04:41Z

doc/api/fs.md

 `fs.readdirSync('c:')`. For more information, see
 [this MSDN page][MSDN-Rel-Path].

+*Note:* On Windows opening existing hidden file using the `w` flag (either


nit: comma after On Windows

jasnell

Almost there. Left a couple comments.

bzoz · 2017-09-18T16:35:09Z

Updated, PTAL

bnoordhuis · 2017-09-21T12:13:53Z

Ping @jasnell. I think your comments have been addressed.

seishun

LGTM otherwise.

seishun · 2017-09-21T12:21:10Z

doc/api/fs.md

+*Note:* On Windows, opening an existing hidden file using the `w` flag (either
+through `fs.open` or `fs.writeFile`) will fail with `EPERM`. Hidden files
+can be opened for writing with either `a` or `r+` flag. A call to
+`fs.truncate` can be used to reset the file contents. 


You can't truncate a file opened in 'a' mode.

> var fd = fs.openSync('test.txt', 'a') undefined > fs.truncateSync(fd) Error: EPERM: operation not permitted, ftruncate

Hm, looks like on Windows you need to open the file with r+ for truncate to work. That is unfortunate, there is no easy way to reproduce Linux behavior. One would need to call truncate with filename, ignore the error if the file does not exists, and then open the file with a parameter.

I guess the best thing is to just document that?

BridgeAR · 2017-10-01T22:22:51Z

@bzoz would you be so kind and address the comment? This is only blocked by that.

bzoz · 2017-10-02T13:27:23Z

Updated, PTAL

seishun · 2017-10-02T13:39:18Z

Rather that opening the file twice, I think we should instead suggest opening in r+ once, then using ftruncate on the fd.

bzoz · 2017-10-02T13:42:00Z

@seishun r+ will fail if the file does not exists.

seishun · 2017-10-02T13:45:42Z

@bzoz fs.truncate will also fail if the file does not exist.

bzoz · 2017-10-02T13:47:34Z

Sure, but then it will be created by fs.open. In the end, after truncate and open with a you will have a empty file opened for writing, even if it existed and was hidden.

seishun · 2017-10-02T13:54:52Z

If we want to suggest only the approach that works for both existing and non-existing files, then "r+" shouldn't be suggested at all. But since people often know beforehand whether the file exists, I would prefer describing both approaches.

bzoz · 2017-10-02T15:48:07Z

Hm, file needs to exist to be "hidden". So maybe we should only describe r+?

bzoz · 2017-10-03T08:05:55Z

Updated. PTAL

seishun · 2017-10-03T08:45:58Z

Since the suggested approach now only works on existing files, perhaps it should say fs.ftruncate instead of fs.truncate, since the fact that the latter works with fds is ~~not~~poorly documented. (I was actually surprised by this behavior, I'm going to submit an issue about it)

BridgeAR · 2017-10-19T05:24:46Z

Landed in 4f1d548

PR-URL: #15409 Fixes: #14553 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Nikolai Vavilov <vvnicholas@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

PR-URL: nodejs/node#15409 Fixes: nodejs/node#14553 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Nikolai Vavilov <vvnicholas@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

doc: document opening hidden files on Windows

4d5ea77

Fixes: nodejs#14553

nodejs-github-bot added doc Issues and PRs related to the documentations. fs Issues and PRs related to the fs subsystem / file system. labels Sep 14, 2017

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reword

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bnoordhuis mentioned this pull request Sep 21, 2017

Can't open hidden files in 'w' mode on Windows - document, fix, or do nothing? #14553

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jasnell approved these changes Sep 21, 2017

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seishun suggested changes Sep 21, 2017

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fixup: clarify truncate call

876d70d

fixup: only r+

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seishun mentioned this pull request Oct 3, 2017

fs.truncate accepts an fd but it's poorly documented #15753

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fixup: ftruncate instead of truncate

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BridgeAR approved these changes Oct 19, 2017

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BridgeAR closed this Oct 19, 2017

MylesBorins added the dont-land-on-v6.x label Nov 16, 2017

vtjnash mentioned this pull request Jun 6, 2022

win: fix EPERM when trying to write a hidden file libuv/libuv#3380

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bzoz commented Sep 14, 2017

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