Dress code for men in Egypt

Dress for the weather, it's dry & hot in Egypt. I wore tshirt and shorts for most of my trip (though I rarely saw locals wear shorts)
Avoid singlets if you can. It's not offensive by any stretch but you'll stand out as no locals wear them
Footwear is flexible (including flip flops), just wear something comfortable
To go into any mosque you'll need to wear pants and something with sleeves
If you plan to do a Nile River cruise bring smart casuals (collared shirts, pants, appropriate shoes)

Let me add a similar brief