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See below for the following code, and below that, the error that follows.

std::string source = "C:\\Users\\cambarchian\\Documents\\tested";
std::string destination = "C:\\Users\\cambarchian\\Documents\\tester";
std::filesystem::path sourcepath = source;
std::filesystem::path destpath = destination;
std::filesystem::copy_options::update_existing;
std::filesystem::copy(sourcepath, destpath);

terminate called after throwing an instance of 'std::filesystem::__cxx11::filesystem_error'
 what():  filesystem error: cannot copy: File exists [C:\Users\cambarchian\Documents\tested] [C:\Users\cambarchian\Documents\tester]

Tried to use filesystem::copy, along with trying different paths. No luck with anything. Not too much I can write here as the problem is listed above, could be a simple formatting issue. That being said, it worked on my home computer using visual studio 2022, however using VS Code with gcc 11.2 gives me this issue.

Christopher Ambarchian
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    The expression `std::filesystem::copy_options::update_existing;` has no effect, and a reasonable compiler would warn you about this. You need the other overload of `copy`. – molbdnilo Apr 05 '22 at 11:16
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    i think you meant to call `copy(sourcepath, destpath, options)`. Voting to close as typo – 463035818_is_not_an_ai Apr 05 '22 at 11:17
  • I put the copy_options within the copy function but it didn't work so I started moving it around, I probably should have mentioned that. Still doesn't work when I write std::filesystem::copy(sourcepath, destpath, std::filesystem::copy_options::recursive); – Christopher Ambarchian Apr 05 '22 at 11:21
  • `recursive`? Don't you want `std::filesystem::copy(sourcepath, destpath, std::filesystem::copy_options::update_existing);` ? – 463035818_is_not_an_ai Apr 05 '22 at 11:25
  • please be careful with details. The code you posted has the same issue also on your home computer. – 463035818_is_not_an_ai Apr 05 '22 at 11:26
  • is the issue perhaps combining `recursive` and `update_existing` ? – 463035818_is_not_an_ai Apr 05 '22 at 11:27
  • It worked without even specifying any copy_options on my home computer, which I guess is why I'm not paying too much care with what I assign to it. Trying recursive and update_existing yields the same issue. – Christopher Ambarchian Apr 05 '22 at 11:29
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    Moving non-working things around arbitrarily, hoping to stumble on to something that works, is one of the least effective methods for solving a problem. – molbdnilo Apr 05 '22 at 11:31

3 Answers3

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Using: filesystem::copy_file(oldPath, newPath, filesystem::copy_options::overwrite_existing);

kaaleksandr
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The overloads of std::filesystem::copy are documented. You're using the first overload, but want the second:

  1. void copy(from, to) which is equivalent to [overload 2, below] using copy_options::none
  2. void copy(from, to, options)

Writing the statement std::filesystem::copy_options::update_existing; before calling copy doesn't achieve anything at all, whereas passing the option to the correct overload like

std::filesystem::copy(sourcepath, destpath,
                      std::filesystem::copy_options::update_existing);

should do what you want.

... it worked on my home computer using visual studio 2022 ...

you don't say whether the destination file existed in that case, which is the first thing you should check.

I put the copy_options within the copy function but it didn't work so I started moving it around, I probably should have mentioned that.

Randomly permuting your code isn't a good way of generating clean examples for others to help with.

In the rare event that hacking away at something does fix it, I strongly recommend pausing to figure out why. When you've hacked away at something and it still doesn't work, by all means leave comments to remind yourself what you tried, but the code itself should still be in a good state.

Still doesn't work when I write std::filesystem::copy(sourcepath, destpath, std::filesystem::copy_options::recursive)

Well, that's a different option, isn't it? Were you randomly permuting which copy_options you selected as well?

Trying recursive and update_existing yields the same issue.

The documentation says

The behavior is undefined if there is more than one option in any of the copy_options option group present in options (even in the copy_file group).

so you shouldn't be setting both anyway. There's no benefit to recursively copying a single file, but there may be a benefit to updating or overwriting one. If the destination already exists. Which, according to your error, it does.

Since you do have an error explicitly saying "File exists", you should certainly look at the "options controlling copy_file() when the file already exists" section of the table here.

Useless
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Visual Studio 2022 fixed the problem

Christopher Ambarchian
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  • Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Apr 05 '22 at 17:24