Io::copy works, but fs::copy fails

help
1

I've run into somewhat unexpected behavior and would like to know if someone already knows what this means.

In my program, at some point, I want to copy existing file into freshly created directory. When I use std::fs::copy, like this:

std::fs::copy(&source, &target)?;

it fails with "Operation not permitted (os error 1)". However, when I open two files and copy between them, like this:

let mut source = std::fs::File::open(&source)?;
let mut target = std::fs::File::create(&target)?;
std::io::copy(&mut source, &mut target)?;

it works. What might be the cause for this difference?

2

The fs::copy operation will also copy various metadata of the file, so it may be failing to copy that.

3

This make sense, since both the source and destination are on the NTFS disk mounted to the Linux system. However, wouldn't the standard cp program fail in this case too?

4

The cp commandline tool might know about NTFS or otherwise know how to better handle copies of metadata. The fs::copy function is not implemented as a call to cp, after all.

5

Running the program under the strace command should help determine exactly what operation is failing.