diff --git a/exec.go b/exec.go
index e18cdd6..726a986 100644
--- a/exec.go
+++ b/exec.go
@@ -323,8 +323,18 @@ func execHandle(bg bool) interp.ExecHandlerFunc {
 			luacmdArgs.Set(rt.IntValue(int64(i + 1)), rt.StringValue(str))
 		}
 
+		hc := interp.HandlerCtx(ctx)
 		if commands[args[0]] != nil {
-			luaexitcode, err := rt.Call1(l.MainThread(), rt.FunctionValue(commands[args[0]]), rt.TableValue(luacmdArgs))
+			stdin := newSinkInput(hc.Stdin)
+			stdout := newSinkOutput(hc.Stdout)
+			stderr := newSinkOutput(hc.Stderr)
+
+			sinks := rt.NewTable()
+			sinks.Set(rt.StringValue("in"), rt.UserDataValue(stdin.ud))
+			sinks.Set(rt.StringValue("out"), rt.UserDataValue(stdout.ud))
+			sinks.Set(rt.StringValue("err"), rt.UserDataValue(stderr.ud))
+
+			luaexitcode, err := rt.Call1(l.MainThread(), rt.FunctionValue(commands[args[0]]), rt.TableValue(luacmdArgs), rt.TableValue(sinks))
 			if err != nil {
 				fmt.Fprintln(os.Stderr, "Error in command:\n" + err.Error())
 				return interp.NewExitStatus(1)
@@ -364,7 +374,6 @@ func execHandle(bg bool) interp.ExecHandlerFunc {
 		killTimeout := 2 * time.Second
 		// from here is basically copy-paste of the default exec handler from
 		// sh/interp but with our job handling
-		hc := interp.HandlerCtx(ctx)
 		path, err := interp.LookPathDir(hc.Dir, hc.Env, args[0])
 		if err != nil {
 			fmt.Fprintln(hc.Stderr, err)
diff --git a/lua.go b/lua.go
index 79eb1f7..0a7c115 100644
--- a/lua.go
+++ b/lua.go
@@ -23,6 +23,7 @@ func luaInit() {
 		MessageHandler: debuglib.Traceback,
 	})
 	lib.LoadAll(l)
+	setupSinkType(l)
 
 	lib.LoadLibs(l, hilbishLoader)
 	// yes this is stupid, i know
diff --git a/nature/commands/cat.lua b/nature/commands/cat.lua
index 132db5f..52e5cda 100644
--- a/nature/commands/cat.lua
+++ b/nature/commands/cat.lua
@@ -1,7 +1,7 @@
 local commander = require 'commander'
 local fs = require 'fs'
 
-commander.register('cat', function(args)
+commander.register('cat', function(args, sinks)
 	local exit = 0
 
 	if #args == 0 then
@@ -17,7 +17,7 @@ usage: cat [file]...]]
 			goto continue
 		end
 
-		io.write(f:read '*a')
+		sinks.out:write(f:read '*a')
 		::continue::
 	end
 	io.flush()
diff --git a/sink.go b/sink.go
new file mode 100644
index 0000000..619c3f8
--- /dev/null
+++ b/sink.go
@@ -0,0 +1,101 @@
+package main
+
+import (
+	"fmt"
+	"io"
+
+	"hilbish/util"
+
+	rt "github.com/arnodel/golua/runtime"
+)
+
+var sinkMetaKey = rt.StringValue("hshsink")
+
+// a sink is a structure that has input and/or output
+// it is like a lua file when used in popen, but specific to hilbish
+type sink struct{
+	writer io.Writer
+	reader io.Reader
+	ud *rt.UserData
+}
+
+func setupSinkType(rtm *rt.Runtime) {
+	sinkMeta := rt.NewTable()
+
+	sinkMethods := rt.NewTable()
+	sinkFuncs := map[string]util.LuaExport{
+		"write": {luaSinkWrite, 2, false},
+	}
+	util.SetExports(l, sinkMethods, sinkFuncs)
+
+	sinkIndex := func(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+		arg := c.Arg(1)
+		val := sinkMethods.Get(arg)
+
+		return c.PushingNext1(t.Runtime, val), nil
+	}
+
+	sinkMeta.Set(rt.StringValue("__index"), rt.FunctionValue(rt.NewGoFunction(sinkIndex, "__index", 2, false)))
+	l.SetRegistry(sinkMetaKey, rt.TableValue(sinkMeta))
+}
+
+func luaSinkWrite(t *rt.Thread, c *rt.GoCont) (rt.Cont, error) {
+	if err := c.CheckNArgs(2); err != nil {
+		return nil, err
+	}
+
+	s, err := sinkArg(c, 0)
+	if err != nil {
+		return nil, err
+	}
+	data, err := c.StringArg(1)
+	if err != nil {
+		return nil, err
+	}
+
+	s.writer.Write([]byte(data))
+
+	return c.Next(), nil
+}
+
+func newSinkInput(r io.Reader) *sink {
+	s := &sink{
+		reader: r,
+	}
+	s.ud = sinkUserData(s)
+
+	return s
+}
+
+func newSinkOutput(w io.Writer) *sink {
+	s := &sink{
+		writer: w,
+	}
+	s.ud = sinkUserData(s)
+
+	return s
+}
+
+func sinkArg(c *rt.GoCont, arg int) (*sink, error) {
+	s, ok := valueToSink(c.Arg(arg))
+	if !ok {
+		return nil, fmt.Errorf("#%d must be a sink", arg + 1)
+	}
+
+	return s, nil
+}
+
+func valueToSink(val rt.Value) (*sink, bool) {
+	u, ok := val.TryUserData()
+	if !ok {
+		return nil, false
+	}
+
+	s, ok := u.Value().(*sink)
+	return s, ok
+}
+
+func sinkUserData(s *sink) *rt.UserData {
+	sinkMeta := l.Registry(sinkMetaKey)
+	return rt.NewUserData(s, sinkMeta.AsTable())
+}