anchor.diff: -{ lib, stdenv, fetchurl, ncurses, pkgconfig }:
  +{ lib, stdenv, fetchurl, ncurses, pkgconfig
  +
  +# procps is mostly Linux-only. Most commands require a running Linux
  +# system (or very similar like that found in Cygwin). The one
  +# exception is ‘watch’ which is portable enough to run on pretty much
  +# any UNIX-compatible system.
  +, watchOnly ? !(stdenv.isLinux || stdenv.isCygwin) }:
   
   stdenv.mkDerivation rec {
     name = "procps-${version}";
  
positive.code:     description = "Utilities that give information about processes using the /proc filesystem";
      priority = 10; # less than coreutils, which also provides "kill" and "uptime"
      license = lib.licenses.gpl2;
      platforms = lib.platforms.linux ++ lib.platforms.cygwin ++ lib.platforms.darwin;
      maintainers = [ lib.maintainers.typetetris ];
    };
  }
  
negative.code:     [ "ac_cv_func_malloc_0_nonnull=yes"
        "ac_cv_func_realloc_0_nonnull=yes" ];
  
    installPhase = if watchOnly then ''
      install -m 0755 -D watch $out/bin/watch
      install -m 0644 -D watch.1 $out/share/man/man1/watch.1
    '' else null;
  