FileSystem.Exists.Unix: eliminate a stat call when checking a non-existing file/directory. #55210
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…sting file/directory. When checking for a directory, we can use `stat`, there is no need to make an `lstat` call. When checking for a file, use `lstat` which will give us what we need in most cases. Only when it is a link, we need to call `stat` to check if the final target is not a directory.
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Tagging subscribers to this area: @dotnet/area-system-io Issue DetailsWhen checking for a directory, we can use When checking for a file, use @adamsitnik @stephentoub ptal.
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| ((fileinfo.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFDIR); | ||
| if ((fileinfo.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFLNK) | ||
| { | ||
| if (Interop.Sys.Stat(fullPath, out fileinfo) < 0) |
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Note that, when the target is a symbolic link, we're now making two calls instead of one.
So, this is an improvement when the API is used more to check for non-existing files, than it is used against links.
| // Something exists at this path. If the caller is asking for a directory, return true if it's | ||
| // a directory and false for everything else. If the caller is asking for a file, return false for | ||
| // a directory and true for everything else. |
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Can you please preserve this comment and extend it to reflect that symbolic links need to be stat'd in order to discard that they are not targeting a directory?
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When checking for a directory, we can use
stat, there is no need to make anlstatcall.When checking for a file, use
lstatwhich will give us what we need in most cases.Only when it is a link, we need to call
statto check if the final target is not a directory.@adamsitnik @stephentoub ptal.