Redoxpkgs is an overlay to allow using Nix to cross-compile packages to Redox.
Install Nix, a declarative build system:
curl -L https://nixos.org/nix/install | sh
Install Cachix, a build cache system:
nix-env -iA cachix -f https://cachix.org/api/v1/install
Enable the Nix Community cache:
cachix use nix-community
To compile cowsay:
nix-build . -A pkgsCross.x86_64-unknown-redox.cowsay
You can also try hexyl or sl.
To install a compiled package onto Redox, copy the /nix/store path at the end of nix-build's stdout onto your Redox filesystem:
redoxfs harddrive.bin /mnt
mkdir -p /mnt/nix/store
cp -r /nix/store/mfhmfarn90g71ysxi7z6iaz07dwjj166-cowsay-3.03+dfsg2-x86_64-unknown-redox /mnt/nix/store
Unmount your filesystem, launch QEMU, and enjoy:
(redox) $ echo 'hi' | /nix/store/mfhmfarn90g71ysxi7z6iaz07dwjj166-cowsay-3.03+dfsg2-x86_64-unknown-redox/bin/cowsay