anchor.diff:        ln -s "${provider}" "$out/bin/${cmd}"
       '';
   
  -in rec {
  -
     # more is unavailable in darwin
     # just use less
     more_compat = runCommand "more" {} ''
  
positive.code: # input, not "procps" which requires Linux.
  
  let
  
    singleBinary = cmd: providers: let
        provider = "${lib.getBin providers.${hostPlatform.parsed.kernel.name}}/bin/${cmd}";
      in runCommand cmd {
  
negative.code:     ln -s ${pkgs.less}/bin/less $out/bin/more
    '';
  
    bins = lib.mapAttrs singleBinary {
      # singular binaries
      arp = {
        linux = pkgs.nettools;
        darwin = pkgs.darwin.network_cmds;
      };
      col = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.text_cmds;
      };
      eject = {
        linux = pkgs.utillinux;
      };
      getopt = {
        linux = pkgs.utillinux;
        darwin = pkgs.getopt;
      };
      fdisk = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.diskdev_cmds;
      };
      fsck = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.diskdev_cmds;
      };
      hexdump = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.shell_cmds;
      };
      hostname = {
        linux = pkgs.nettools;
        darwin = pkgs.darwin.shell_cmds;
      };
      ifconfig = {
        linux = pkgs.nettools;
        darwin = pkgs.darwin.network_cmds;
      };
      logger = {
        linux = pkgs.utillinux;
      };
      more = {
        linux = pkgs.utillinux;
        darwin = more_compat;
      };
      mount = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.diskdev_cmds;
      };
      netstat = {
        linux = pkgs.nettools;
        darwin = pkgs.darwin.network_cmds;
      };
      ping = {
        linux = pkgs.iputils;
        darwin = pkgs.darwin.network_cmds;
      };
      ps = {
        linux = pkgs.procps;
        darwin = pkgs.darwin.ps;
      };
      quota = {
        linux = pkgs.linuxquota;
        darwin = pkgs.darwin.diskdev_cmds;
      };
      route = {
        linux = pkgs.nettools;
        darwin = pkgs.darwin.network_cmds;
      };
      script = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.shell_cmds;
      };
      sysctl = {
        linux = pkgs.procps;
        darwin = pkgs.darwin.system_cmds;
      };
      top = {
        linux = pkgs.procps;
        darwin = pkgs.darwin.top;
      };
      umount = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.diskdev_cmds;
      };
      whereis = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.shell_cmds;
      };
      wall = {
        linux = pkgs.utillinux;
      };
      write = {
        linux = pkgs.utillinux;
        darwin = pkgs.darwin.basic_cmds;
      };
    };
  
    makeCompat = name': value: buildEnv {
        name = name' + "-compat";
        paths = value;
    };
  
    # Compatibility derivations
    # Provided for old usage of these commands.
    compat = with bins; lib.mapAttrs makeCompat {
      procps = [ ps sysctl top ];
      utillinux = [ fsck fdisk getopt hexdump mount
                    script umount whereis write col ];
      nettools = [ arp hostname ifconfig netstat route ];
    };
  in bins // compat
  