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