C# xattr file attributes

Question

I'm creating a cross-platform software and I want to know if there is any (easy) way to read/write Unix (Mac OSX/Linux) extended file attributes in C#. I've just read about xattr namespaces, but I haven't found any information about C# implementation or bindings of this feature.

P.S. The only thing I found so far is python-xattr library, but I don't want to use it because:

• I don't want to obligate the users to install Python (there is already Mono/.NET dependency to deal with)
• By using Python I will have a performance decrease (C# is compiled, while Python is interpreted)
• I don't want to rely/depend on external tools (if it's possible), because it's not safe

Answer 1

You should use the syscalls in Mono.Unix.Native.Syscall.*attr*.
The nuget assembly is called Mono.Posix.NETStandard

Note that the name of the name-value pair is prefixed with a namespace.
According to man 7 xattr

Currently, the security, system, trusted, and user extended attribute classes are defined as described below. Additional classes may be added in the future.

public static void Test()
{
    string path = "/root/Desktop/CppSharp.txt";

    // Mono.Unix.Native.Syscall.getxattr()
    // Mono.Unix.Native.Syscall.fgetxattr()
    // Mono.Unix.Native.Syscall.lgetxattr()

    // Mono.Unix.Native.Syscall.setxattr()
    // Mono.Unix.Native.Syscall.fsetxattr()
    // Mono.Unix.Native.Syscall.lsetxattr

    // Mono.Unix.Native.Syscall.llistxattr()
    // Mono.Unix.Native.Syscall.flistxattr()
    // Mono.Unix.Native.Syscall.llistxattr()

    // Mono.Unix.Native.Syscall.removexattr()
    // Mono.Unix.Native.Syscall.fremovexattr()
    // Mono.Unix.Native.Syscall.lremovexattr()

    if (System.IO.File.Exists(path))
        System.Console.WriteLine("path exists");
    else
        System.Console.WriteLine("path doesn't exists");

    System.Text.Encoding enc = new System.Text.UTF8Encoding(false);
    string[] values = null;

    int setXattrSucceeded = Mono.Unix.Native.Syscall.setxattr(path, "user.foobar",
        enc.GetBytes("Hello World äöüÄÖÜ"), Mono.Unix.Native.XattrFlags.XATTR_CREATE);

    if (setXattrSucceeded == -1)
    {
        Mono.Unix.Native.Errno er = Mono.Unix.Native.Stdlib.GetLastError();
        string message = Mono.Unix.Native.Stdlib.strerror(er);
        // https://stackoverflow.com/questions/12662765/how-can-i-get-error-message-for-errno-value-c-language
        System.Console.WriteLine(message);
    } // End if (setXattrSucceeded == -1)

    byte[] data = null;
    long szLen = Mono.Unix.Native.Syscall.getxattr(path, "user.foobar", out data);

    string value = enc.GetString(data);
    System.Console.WriteLine(value);

    Mono.Unix.Native.Syscall.listxattr(path, System.Text.Encoding.UTF8, out values);
    System.Console.WriteLine(values);

    // https://man7.org/linux/man-pages/man2/getxattr.2.html
} // End Sub TestExtendedAttributes