Code shared from run.dlang.io. Run with '-unittest'

main.d

void main()
{
    import std.algorithm, std.stdio, std.file, std.range;
    enum cols = 14;
    // Split file into 14-byte chunks per row
    thisExePath.File("rb").byChunk(cols).take(20).each!(chunk =>
        // Use range formatting to format the
        // hexadecimal part and align the text part
        writefln!"%(%02X %)%*s  %s"(
            chunk,
            20, "xxxx",
            //3 * (cols - chunk.length), "", // Padding
            map!(c => // Replace non-printable
                c < 0x20 || c > 0x7E ? '.' : char(c))(chunk)));
}