anchor.diff:      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;
  
positive.code:   sysctl = singleBinary "sysctl" {
      linux = pkgs.procps;
      darwin = pkgs.darwin.system_cmds;
    };
    umount = singleBinary "umount" {
      linux = pkgs.utillinux;
  
negative.code: 
    procps = buildEnv {
      name = "procps-compat";
      paths = [ ps sysctl top ];
    };
  
    utillinux = buildEnv {
      name = "utillinux-compat";
      paths = [ fsck fdisk getopt hexdump mount
                quota script umount whereis write ];
    };
  
    nettools = buildEnv {
      name = "nettools-compat";
      paths = [ arp hostname ifconfig netstat route ];
    };
  }
  