diff --git a/include/bed.h b/include/bed.h
index ab2b0ef..1e6e7e3 100644
--- a/include/bed.h
+++ b/include/bed.h
@@ -4,11 +4,11 @@
 #include "internal/buffer/buffer.h"
 #include "internal/functions/functions.h"
 #include "internal/functions/suffixes.h"
-#include "internal/io/command.h"
 #include "internal/io/io.h"
 #include "internal/marks/marks.h"
 #include "internal/theme/theme.h"
 #include "internal/ui/autocomp.h"
+#include "internal/ui/command.h"
 #include "pch.h"
 
 namespace bed {
@@ -27,6 +27,7 @@ struct BEd {
   bool prompt_mode = true;
   std::function<std::string(BEd &)> prompt = nullptr;
   bool suppress_mode = false;
+  bool temporary_current = false;
   std::string last_regex = "";
   std::string last_symbol = "";
   std::string last_replacement = "";
diff --git a/include/internal/buffer/buffer.h b/include/internal/buffer/buffer.h
index c06798b..9423430 100644
--- a/include/internal/buffer/buffer.h
+++ b/include/internal/buffer/buffer.h
@@ -25,6 +25,8 @@ struct Buffer {
   ~Buffer();
 
   uint64_t lines();
+  uint64_t bytes();
+  void load(BEd &ctx, vase::Shard *text);
   vase::Shard *copy(uint64_t start_line, uint64_t end_line);
   void substitute(
     BEd &ctx, uint64_t start_line, uint64_t end_line,
diff --git a/include/internal/io/io.h b/include/internal/io/io.h
index 9ab91e6..296e07e 100644
--- a/include/internal/io/io.h
+++ b/include/internal/io/io.h
@@ -50,6 +50,14 @@ struct KeyEvent {
 };
 
 struct IO {
+  static termios orig_termios;
+  static termios raw_termios;
+  static bool cleaned;
+  static void cleanup();
+  static void enable_raw();
+  static volatile std::atomic_bool resized;
+  static void handle_sigwinch(int);
+
   IO();
   ~IO();
 
@@ -70,13 +78,6 @@ struct IO {
   void write(const char *, uint64_t);
   void write(std::string_view);
 
-private:
-  static termios orig_termios;
-  static bool cleaned;
-  static void cleanup();
-  static volatile std::atomic_bool resized;
-  static void handle_sigwinch(int);
-
   std::deque<char> input_queue;
 
   KeyEvent::ReadResult get_next_byte(char &out);
diff --git a/include/internal/marks/marks.h b/include/internal/marks/marks.h
index 13fbf03..ddc5bd3 100644
--- a/include/internal/marks/marks.h
+++ b/include/internal/marks/marks.h
@@ -48,8 +48,8 @@ struct MarksEngine {
         continue;
       if (marks[i].number == UINT64_MAX)
         continue;
-      if (marks[i].number >= start) {
-        if (marks[i].number < start + count)
+      if (marks[i].number > start) {
+        if (marks[i].number <= start + count)
           marks[i].number = start;
         else
           marks[i].number -= count;
diff --git a/include/internal/parser/parser.h b/include/internal/parser/parser.h
index 2e76992..033187f 100644
--- a/include/internal/parser/parser.h
+++ b/include/internal/parser/parser.h
@@ -2,7 +2,7 @@
 
 #include "internal/functions/functions.h"
 #include "internal/functions/suffixes.h"
-#include "internal/io/command.h"
+#include "internal/ui/command.h"
 #include "pch.h"
 
 namespace bed::internal::parser {
@@ -85,12 +85,12 @@ struct Parser {
   std::string_view cmd;
   uint16_t i;
   Command *command;
-  std::vector<io::Token> *tokens;
+  std::vector<ui::Token> *tokens;
   CompletionContext *completion;
 
   explicit Parser(
     std::string_view cmd, BEd &bed, Command *command,
-    std::vector<io::Token> *tokens, CompletionContext *completion
+    std::vector<ui::Token> *tokens, CompletionContext *completion
   );
 
   char peek(uint16_t = 0); // == \0 if at eof.
diff --git a/include/internal/syntax/parser.h b/include/internal/syntax/parser.h
index db6a6a6..a39e571 100644
--- a/include/internal/syntax/parser.h
+++ b/include/internal/syntax/parser.h
@@ -5,8 +5,6 @@
 #include "pch.h"
 
 namespace bed::internal::syntax {
-void dump_events(ParseState *node);
-
 struct Parser {
   static constexpr uint64_t MAX_CHUNK = 512;
 
diff --git a/include/internal/io/command.h b/include/internal/ui/command.h
similarity index 88%
rename from include/internal/io/command.h
rename to include/internal/ui/command.h
index a75a1ab..5e5742b 100644
--- a/include/internal/io/command.h
+++ b/include/internal/ui/command.h
@@ -4,7 +4,7 @@
 #include "internal/ui/autocomp.h"
 #include "pch.h"
 
-namespace bed::internal::io {
+namespace bed::internal::ui {
 struct Token {
   enum struct Type : uint8_t {
     TempCurrent,      // @
@@ -39,10 +39,10 @@ struct CommandIO {
   uint16_t term_height;
   uint16_t term_width;
   BEd &bed;
-  IO &io;
+  io::IO &io;
 
-  CommandIO(BEd &, IO &);
+  CommandIO(BEd &, io::IO &);
   std::pair<std::string, bool> run();
   void redraw();
 };
-} // namespace bed::internal::io
+} // namespace bed::internal::ui
diff --git a/include/internal/vase/shard.h b/include/internal/vase/shard.h
index 9677812..d55debd 100644
--- a/include/internal/vase/shard.h
+++ b/include/internal/vase/shard.h
@@ -27,14 +27,12 @@ struct Shard {
   static Shard *from_file(const std::filesystem::path &path, bool posix_ending);
   static Shard *from_string(const char *data, uint64_t len, bool posix_ending);
   static Shard *from_command(const char *cmd, bool posix_ending);
-  // static std::vector<Shard *> from_swap(std::filesystem::path &path, OriginalStorage *b);
 
   static std::pair<Shard *, Shard *> split(Shard *n, uint64_t offset);
   static Shard *concat(Shard *a, Shard *b);
   static Shard *merge_leaves(Shard *a, Shard *b);
   static Shard *append(Shard *root, Shard *leaf);
   static Shard *build(Shard **pieces, uint64_t lo, uint64_t hi);
-  static void dump(Shard *node, int depth = 0);
 };
 
 struct Branch : Shard {
diff --git a/include/internal/vase/vase.h b/include/internal/vase/vase.h
index 3fecc90..8d5f12f 100644
--- a/include/internal/vase/vase.h
+++ b/include/internal/vase/vase.h
@@ -48,6 +48,7 @@ std::string to_string(Shard *root, Range range);
 
 Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line);
 Shard *erase(Shard *root, uint64_t start, uint64_t end);
+Shard *join(Shard *root, uint64_t start, uint64_t end);
 Shard *copy(Shard *root, uint64_t start, uint64_t end);
 
 uint64_t find_next(Shard *root, std::string_view pattern, uint64_t start);
diff --git a/src/bed/run.cc b/src/bed/run.cc
index cf22e33..6104575 100644
--- a/src/bed/run.cc
+++ b/src/bed/run.cc
@@ -64,37 +64,41 @@ void BEd::handle(std::string_view cmd, bool eof) {
     return;
   }
   internal::parser::Command c = internal::parser::Parser::get_command(cmd, *this);
+  if (c.temp_address) {
+    marks.get(251) = marks.get(250);
+    temporary_current = true;
+  }
   internal::buffer::Address address;
   switch (c.function->address_kind) {
   case internal::functions::Function::AddressKind::None: {
     auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
-    if (a.has_value()) {
-      address = a->buffername;
-    } else {
+    if (!a.has_value()) {
       auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
       a = internal::parser::AddressPromise::get_line(*this, vec);
-      address = a->buffername;
+      if (!a.has_value())
+        a = current();
     }
+    address = a->buffername;
   } break;
   case internal::functions::Function::AddressKind::Line: {
     auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
-    if (a.has_value()) {
-      address = *a;
-    } else {
+    if (!a.has_value()) {
       auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
       a = internal::parser::AddressPromise::get_line(*this, vec);
-      address = *a;
+      if (!a.has_value())
+        a = current();
     }
+    address = *a;
   } break;
   case internal::functions::Function::AddressKind::Range: {
     auto a = internal::parser::AddressPromise::get_range(*this, c.addresses);
-    if (a.has_value()) {
-      address = *a;
-    } else {
+    if (!a.has_value()) {
       auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
       a = internal::parser::AddressPromise::get_range(*this, vec);
-      address = *a;
+      if (!a.has_value())
+        a = internal::buffer::Range(current(), current());
     }
+    address = *a;
   } break;
   }
   if (std::holds_alternative<internal::buffer::Line>(c.argument)) {
@@ -110,12 +114,36 @@ void BEd::handle(std::string_view cmd, bool eof) {
     else
       c.argument = internal::buffer::Range(current(), current());
   }
+  if (!c.function->accept_zero) {
+    if (std::holds_alternative<internal::buffer::Line>(address)) {
+      if (std::get<internal::buffer::Line>(address).number == 0)
+        throw ed_error("Line number can't be zero.");
+    } else if (std::holds_alternative<internal::buffer::Range>(address)) {
+      auto r = std::get<internal::buffer::Range>(address);
+      if (r.start == 0 || r.end == 0)
+        throw ed_error("Line number can't be zero.");
+    }
+  }
   c.function->handle(*this, address, nullptr, c.argument, nullptr);
   if (c.suffix)
     c.suffix->handle(*this);
+  if (c.temp_address)
+    temporary_current = false;
+  for (auto it = buffers.begin(); it != buffers.end();) {
+    internal::buffer::Buffer *buf = it->second;
+    if (buf->save_path.empty()
+        && buf->root == nullptr) {
+      delete buf;
+      it = buffers.erase(it);
+    } else {
+      ++it;
+    }
+  }
 }
 
 internal::buffer::Buffer &BEd::buffer(const std::string &name) {
+  if (name.empty())
+    throw ed_error("can't have empty buffer name");
   auto it = buffers.find(name);
   if (it != buffers.end())
     return *it->second;
@@ -125,7 +153,7 @@ internal::buffer::Buffer &BEd::buffer(const std::string &name) {
 }
 
 internal::buffer::Line &BEd::current() {
-  return marks.get(250);
+  return marks.get(250 + temporary_current);
 }
 
 void BEd::mark(char m, internal::buffer::Line line) {
diff --git a/src/internal/buffer/buffer.cc b/src/internal/buffer/buffer.cc
index 853bdc0..9a56cd8 100644
--- a/src/internal/buffer/buffer.cc
+++ b/src/internal/buffer/buffer.cc
@@ -4,7 +4,6 @@
 namespace bed::internal::buffer {
 Buffer::Buffer(std::string name)
     : state(Unmodified), root(nullptr), name(name) {
-  parser.emplace(root, lines(), syntax::ruby::lang_ruby()); // just for debug.
 }
 
 Buffer::~Buffer() {
@@ -17,6 +16,24 @@ uint64_t Buffer::lines() {
   return 0;
 }
 
+uint64_t Buffer::bytes() {
+  if (root)
+    return root->length + 1;
+  return 0;
+}
+
+void Buffer::load(BEd &, vase::Shard *text) {
+  try {
+    vase::Shard::release(root);
+    root = text;
+    state = buffer::Buffer::Unmodified;
+    parser.emplace(root, lines(), syntax::ruby::lang_ruby());
+  } catch (...) {
+    vase::Shard::release(text);
+    throw;
+  }
+}
+
 void Buffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
   ctx.prev.buffername = name;
   ctx.prev.start = line;
@@ -31,8 +48,8 @@ void Buffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
 void Buffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
   root = vase::erase(root, start_line, end_line);
   ctx.prev.buffername = name;
-  ctx.prev.start = start_line;
-  ctx.prev.end = start_line;
+  ctx.prev.start = lines() ? 1 : 0;
+  ctx.prev.end = lines();
   ctx.marks.erase(name, start_line, end_line - start_line + 1);
   if (parser)
     parser->erase(root, start_line, end_line - start_line + 1);
@@ -40,7 +57,7 @@ void Buffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
 }
 
 void Buffer::join(BEd &ctx, uint64_t start_line, uint64_t end_line) {
-  root = vase::substitute(&ctx.append, root, R"(\n)", start_line, end_line, "", "g");
+  root = vase::join(root, start_line, end_line);
   ctx.prev.buffername = name;
   ctx.prev.start = start_line;
   ctx.prev.end = start_line;
@@ -54,7 +71,7 @@ void Buffer::substitute(
   BEd &ctx, uint64_t start_line, uint64_t end_line,
   std::string &regex, std::string &replacement, std::string &options
 ) {
-  // make substitue return a list of modifications made.
+  // TODO: make substitue return a list of modifications made.
   root = vase::substitute(&ctx.append, root, regex, start_line, end_line, replacement, options);
   /*prev_range.start = start_line;
   prev_range.end = start_line;
diff --git a/src/internal/functions/functions.cc b/src/internal/functions/functions.cc
index df22d8d..7d2dd39 100644
--- a/src/internal/functions/functions.cc
+++ b/src/internal/functions/functions.cc
@@ -150,12 +150,13 @@ void Function::register_posix(BEd &ctx) {
       .default_address = "$",
       .accept_zero = true,
       .pre_text_mode = nullptr,
-      .handle = [](BEd &, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+      .handle = [](BEd &ctx, const buffer::Address &addr_, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
         auto addr = std::get<buffer::Range>(addr_);
         if (addr.start == addr.end)
           std::cout << ':' << addr.buffername << ':' << addr.start << "\n";
         else
           std::cout << ':' << addr.buffername << ':' << addr.start << "," << addr.end << "\n";
+        ctx.current() = {addr.buffername, addr.end};
       },
     }
   );
@@ -204,17 +205,8 @@ void Function::register_posix(BEd &ctx) {
           else
             throw ed_error("Need filename to load.");
         }
-        try {
-          if (buf.lines())
-            buf.remove(ctx, 1, buf.lines());
-          buf.append(ctx, s, 0);
-          buf.state = buffer::Buffer::Unmodified;
-        } catch (...) {
-          vase::Shard::release(s);
-          throw;
-        }
-        std::cout << (s->length + 1) << std::endl;
-        vase::Shard::release(s);
+        buf.load(ctx, s);
+        std::cout << buf.bytes() << std::endl;
         ctx.current() = {addr, buf.lines()};
       }
     }
@@ -244,17 +236,8 @@ void Function::register_posix(BEd &ctx) {
           else
             throw ed_error("Need filename to load.");
         }
-        try {
-          if (buf.lines())
-            buf.remove(ctx, 1, buf.lines());
-          buf.append(ctx, s, 0);
-          buf.state = buffer::Buffer::Unmodified;
-        } catch (...) {
-          vase::Shard::release(s);
-          throw;
-        }
-        std::cout << (s->length + 1) << std::endl;
-        vase::Shard::release(s);
+        buf.load(ctx, s);
+        std::cout << buf.bytes() << std::endl;
         ctx.current() = {addr, buf.lines()};
       }
     }
@@ -291,5 +274,23 @@ void Function::register_posix(BEd &ctx) {
       }
     }
   );
+  ctx.functions.insert(
+    "P",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Toggle prompt.",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](BEd &ctx, const buffer::Address &, vase::Shard *, const Argument &, std::vector<buffer::Line> *) {
+        ctx.prompt_mode = !ctx.prompt_mode;
+        if (ctx.prompt_mode && !ctx.prompt) {
+          ctx.prompt = [](BEd &) { return "*"; };
+        }
+      }
+    }
+  );
 }
 } // namespace bed::internal::functions
diff --git a/src/internal/io/_command.cc b/src/internal/io/_command.cc
deleted file mode 100644
index 18d37c2..0000000
--- a/src/internal/io/_command.cc
+++ /dev/null
@@ -1,10 +0,0 @@
-#include "bed.h"
-#include "internal/io/command.h"
-#include "internal/io/io.h"
-
-namespace bed::internal::io {
-std::pair<std::string, bool> IO::get_command(BEd &ctx) {
-  CommandIO cio(ctx, *this);
-  return cio.run();
-}
-} // namespace bed::internal::io
diff --git a/src/internal/io/command.cc b/src/internal/io/command.cc
index b6e02eb..ab6fe3f 100644
--- a/src/internal/io/command.cc
+++ b/src/internal/io/command.cc
@@ -1,156 +1,10 @@
+#include "internal/ui/command.h"
 #include "bed.h"
+#include "internal/io/io.h"
 
 namespace bed::internal::io {
-/*template <typename F>
-static void for_each_cluster(std::string_view s, F &&f) {
-  unicode_width_state_t state;
-  unicode_width_init(&state);
-  size_t i = 0;
-  while (i < s.size()) {
-    unsigned char c = static_cast<unsigned char>(s[i]);
-    size_t bytes = 1;
-    int width = 0;
-    if (c < 128) {
-      width = unicode_width_process(&state, c);
-    } else {
-      uint_least32_t cp;
-      size_t decoded = grapheme_decode_utf8(s.data() + i, s.size() - i, &cp);
-      bytes = decoded > 0 ? decoded : 1;
-      width = unicode_width_process(&state, cp);
-    }
-    if (width < 0)
-      width = 0;
-    f(i, bytes, width);
-    i += bytes;
-  }
-}
-
-static int display_width(std::string_view s) {
-  int w = 0;
-  for_each_cluster(s, [&](size_t, size_t, int cw) { w += cw; });
-  return w;
-}
-
-static uint16_t count_clusters(std::string_view s) {
-  uint16_t n = 0;
-  for_each_cluster(s, [&](size_t, size_t, int) { ++n; });
-  return n;
-}
-
-static std::vector<uint16_t> wrap_offsets(std::string_view line, uint16_t avail) {
-  std::vector<uint16_t> offsets{0};
-  int col = 0;
-  for_each_cluster(line, [&](uint16_t i, uint16_t, int w) {
-    if (col + w > avail && col > 0) {
-      offsets.push_back(i);
-      col = 0;
-    }
-    col += w;
-  });
-  return offsets;
-}
-
-// The word under/before `byte_pos`, split on plain ASCII spaces. Used to
-// pick what prefix to hand the suggestion trie.
-// TODO: change to use libgrapheme word break here.
-static std::string current_word(const std::string &line, size_t byte_pos) {
-  size_t start = (byte_pos == 0) ? std::string::npos : line.rfind(' ', byte_pos - 1);
-  start = (start == std::string::npos) ? 0 : start + 1;
-  if (byte_pos < start)
-    byte_pos = start;
-  return line.substr(start, byte_pos - start);
-}*/
-
-CommandIO::CommandIO(BEd &bed, IO &io) : bed(bed), io(io) {
-  prompt = bed.prompt(bed);
-  cursor = 0;
-}
-
-std::pair<std::string, bool> CommandIO::run() {
-  auto [row, col] = io.cursor_position();
-  auto [rows, cols] = io.terminal_size();
-  if (row > rows)
-    throw fatal_error("Invalid cursor position.", 1);
-  start = row;
-  height = rows - row + 1;
-  term_width = cols;
-  term_height = rows;
-  redraw();
-
-  // main loop.
-  KeyEvent res;
-  bool running = true;
-  while (running) {
-    res = io.read_key();
-    switch (res.type) {
-    case KeyEvent::KeyType::EOF_:
-      running = false;
-      break;
-    case KeyEvent::KeyType::MOUSE:
-    case KeyEvent::KeyType::RESIZE:
-      break;
-    case KeyEvent::KeyType::CHAR:
-      switch (res.modifier) {
-      case KeyEvent::Modifier::SHIFT:
-      case KeyEvent::Modifier::ALT:
-      case KeyEvent::Modifier::CTRL_ALT:
-      case KeyEvent::Modifier::CTRL:
-        break;
-      case KeyEvent::Modifier::NONE:
-        if (res.text[0] == '\b' || res.text[0] == 0x7f) {
-          if (cursor > 0)
-            cmd.erase(--cursor, 1);
-        } else if (res.text[0] == '\n') {
-          running = false;
-        } else {
-          cmd.insert(cursor++, res.text);
-        }
-        break;
-      }
-      break;
-    case KeyEvent::KeyType::PASTE:
-      cmd.insert(cursor, res.text);
-      cursor += res.text.size();
-      break;
-    case KeyEvent::KeyType::SPECIAL:
-      switch (res.special_key) {
-      case KeyEvent::SpecialKey::UNKNOWN:
-      case KeyEvent::SpecialKey::UP:
-      case KeyEvent::SpecialKey::DOWN:
-        break;
-      case KeyEvent::SpecialKey::RIGHT:
-        if (cursor < cmd.size())
-          cursor++;
-        break;
-      case KeyEvent::SpecialKey::LEFT:
-        if (cursor > 0)
-          cursor--;
-        break;
-      case KeyEvent::SpecialKey::DELETE:
-        if (cursor < cmd.size())
-          cmd.erase(cursor, 1);
-        break;
-      }
-      break;
-    }
-    redraw();
-  }
-
-  for (uint16_t i = 1; i < height; ++i) {
-    io.move_cursor(start + i, 1);
-    io.write("\x1b[2K", 4);
-  }
-  io.move_cursor(start, 1);
-  io.write("\n", 1);
-  return {cmd, false};
-}
-
-void CommandIO::redraw() {
-  io.move_cursor(start, 1);
-  io.write("\x1b[2K", 4);
-  io.move_cursor(start, 1);
-  io.write(prompt);
-  io.write(cmd);
-  io.move_cursor(start, prompt.size() + cursor + 1);
+std::pair<std::string, bool> IO::get_command(BEd &ctx) {
+  ui::CommandIO cio(ctx, *this);
+  return cio.run();
 }
 } // namespace bed::internal::io
diff --git a/src/internal/io/io.cc b/src/internal/io/io.cc
index a7d7d6f..72b9d4f 100644
--- a/src/internal/io/io.cc
+++ b/src/internal/io/io.cc
@@ -2,7 +2,8 @@
 
 namespace bed::internal::io {
 termios IO::orig_termios{};
-bool IO::cleaned = false;
+termios IO::raw_termios{};
+bool IO::cleaned = true;
 volatile std::atomic_bool IO::resized(false);
 
 IO::IO() {
@@ -14,16 +15,13 @@ IO::IO() {
   sa.sa_flags = 0;
   if (sigaction(SIGWINCH, &sa, nullptr) == -1)
     throw fatal_error("Can't install SIGWINCH handler.", 1);
-  struct termios raw = orig_termios;
-  raw.c_iflag &= ~(BRKINT | ISTRIP | IXON);
-  raw.c_cflag |= (CS8);
-  raw.c_lflag &= ~(ECHO | ICANON | ISIG);
-  raw.c_cc[VMIN] = 1;
-  raw.c_cc[VTIME] = 0;
-  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1)
-    throw fatal_error("Can't set terminal state.", 1);
-  std::string os = "\x1b[?2004h";
-  write_all(STDOUT_FILENO, os.c_str(), os.size());
+  raw_termios = orig_termios;
+  raw_termios.c_iflag &= ~(BRKINT | ISTRIP | IXON);
+  raw_termios.c_cflag |= (CS8);
+  raw_termios.c_lflag &= ~(ECHO | ICANON | ISIG);
+  raw_termios.c_cc[VMIN] = 1;
+  raw_termios.c_cc[VTIME] = 0;
+  enable_raw();
   atexit(cleanup);
 }
 
@@ -70,6 +68,16 @@ std::pair<uint16_t, uint16_t> IO::cursor_position() {
   return {(uint16_t)row, (uint16_t)col};
 }
 
+void IO::enable_raw() {
+  if (!cleaned)
+    return;
+  std::string os = "\x1b[?2004h";
+  write_all(STDOUT_FILENO, os.c_str(), os.size());
+  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw_termios) == -1)
+    throw fatal_error("Can't set raw terminal state.", 1);
+  cleaned = false;
+}
+
 void IO::cleanup() {
   if (cleaned)
     return;
diff --git a/src/internal/parser/address.cc b/src/internal/parser/address.cc
new file mode 100644
index 0000000..424b097
--- /dev/null
+++ b/src/internal/parser/address.cc
@@ -0,0 +1,252 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed::internal::parser {
+void Parser::locator(AddressPromise &addr) {
+  addr.base = AddressPromise::None{};
+  switch (peek()) {
+  case '.':
+    advance();
+    addr.base = AddressPromise::Current{};
+    break;
+  case '$':
+    advance();
+    addr.base = AddressPromise::Last{};
+    break;
+  case '%':
+    advance();
+    addr.base = AddressPromise::LastRange{};
+    break;
+  case '[':
+    advance();
+    addr.base = AddressPromise::Block{Direction::Backward};
+    break;
+  case ']':
+    advance();
+    addr.base = AddressPromise::Block{Direction::Forward};
+    break;
+  case '^':
+    advance();
+    addr.base = AddressPromise::Diagnostic{Direction::Backward};
+    break;
+  case '~':
+    advance();
+    addr.base = AddressPromise::Diagnostic{Direction::Forward};
+    break;
+  case '\'':
+    advance();
+    if (('a' <= peek() && peek() <= 'z')
+        || ('A' <= peek() && peek() <= 'Z'))
+      addr.base = AddressPromise::Mark{peek()};
+    else
+      throw ed_error("Valid mark needed after \'");
+    advance();
+    break;
+  case '{': {
+    advance();
+    uint16_t j = 0;
+    std::string func;
+    std::string arg;
+    while (peek(j) != '}') {
+      if (peek(j) == '\0')
+        throw ed_error("Scripted address not terminated");
+      if (peek(j) == '\\')
+        ++j;
+      if (peek(j) == ':') {
+        func = peek_str(j);
+        advance(j + 1);
+        j = 0;
+        continue;
+      }
+      ++j;
+    }
+    if (func.size())
+      arg = peek_str(j);
+    else
+      func = peek_str(j);
+    addr.base = AddressPromise::Scripted{std::move(func), std::move(arg)};
+    advance(j + 1);
+  } break;
+  case '/': {
+    advance();
+    uint64_t j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        break;
+      if (peek(j) == '/')
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && cmd[i] != ']')
+          j++;
+      else
+        j++;
+    }
+    addr.base = AddressPromise::Regex(
+      Direction::Forward,
+      std::string(peek_str(j))
+    );
+    advance(j + 1);
+  } break;
+  case '?': {
+    advance();
+    uint16_t j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        break;
+      if (peek(j) == '?')
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && cmd[i] != ']')
+          j++;
+      else
+        j++;
+    }
+    addr.base = AddressPromise::Regex(
+      Direction::Backward,
+      std::string(peek_str(j))
+    );
+    advance(j + 1);
+  } break;
+  case '<': {
+    advance();
+    uint16_t j = 0;
+    while (peek(j) != '>'
+           && peek(j) != '<'
+           && peek(j) != '\0')
+      j++;
+    switch (peek(j)) {
+    case '\0':
+    case '>':
+      addr.base = AddressPromise::SymbolDefinition{
+        std::string(peek_str(j))
+      };
+      break;
+    case '<':
+      addr.base = AddressPromise::SymbolReference{
+        Direction::Backward,
+        std::string(peek_str(j))
+      };
+      break;
+    }
+    advance(j + 1);
+  } break;
+  case '>': {
+    advance();
+    uint16_t j = 0;
+    while (peek(j) != '>' && peek(j) != '\0')
+      j++;
+    switch (peek(j)) {
+    case '\0':
+      throw ed_error("Unterminated symbol reference addressing.");
+    case '>':
+      addr.base = AddressPromise::SymbolReference{
+        Direction::Forward,
+        std::string(peek_str(j))
+      };
+      break;
+    }
+    advance(j + 1);
+  } break;
+  case '+': {
+    advance();
+    addr.base = AddressPromise::Current{};
+    uint16_t j = 0;
+    uint64_t num = 0;
+    while ('0' <= peek(j) && peek(j) <= '9') {
+      num = num * 10 + (peek(j) - '0');
+      j++;
+    }
+    if (j == 0)
+      num = 1;
+    advance(j);
+    addr.offset += num;
+  } break;
+  case '-': {
+    advance();
+    addr.base = AddressPromise::Current{};
+    uint16_t j = 0;
+    uint64_t num = 0;
+    while ('0' <= peek(j) && peek(j) <= '9') {
+      num = num * 10 + (peek(j) - '0');
+      j++;
+    }
+    if (j == 0)
+      num = 1;
+    advance(j);
+    addr.offset -= num;
+  } break;
+  default:
+    if ('0' <= peek() && peek() <= '9') {
+      uint64_t num = 0;
+      while ('0' <= peek() && peek() <= '9') {
+        num = num * 10 + (peek() - '0');
+        advance();
+      }
+      addr.base = AddressPromise::Number{num};
+    }
+  }
+}
+
+int64_t Parser::offset() {
+  int64_t offset = 0;
+  while (peek() == '+' || peek() == '-'
+         || ('0' <= peek() && peek() <= '9')) {
+    bool positive = peek() != '-';
+    if (peek() == '+' || peek() == '-')
+      advance();
+    uint16_t j = 0;
+    int64_t num = 0;
+    while ('0' <= peek(j) && peek(j) <= '9')
+      num = num * 10 + (peek(j++) - '0');
+    if (j == 0)
+      num = 1;
+    advance(j);
+    offset += positive ? num : -num;
+    skip_ws();
+  }
+  skip_ws();
+  return offset;
+}
+
+void Parser::address(AddressPromise &addr) {
+  if (peek() == ':') {
+    advance();
+    uint16_t j = 0;
+    while (peek(j) != ':' && peek(j) != '\0')
+      j++;
+    addr.bufname = peek_str(j);
+    advance(j);
+    if (peek() == ':')
+      advance();
+  }
+  skip_ws();
+  if (peek() == '\0')
+    return;
+  locator(addr);
+  skip_ws();
+  addr.offset += offset();
+}
+
+void Parser::addresses(std::vector<AddressPromise> &addresses) {
+  skip_ws();
+  addresses.push_back({});
+  auto *addr = &addresses.back();
+  address(*addr);
+  while (peek() == ',' || peek() == ';') {
+    addr->jumping = peek() == ';';
+    advance();
+    skip_ws();
+    addresses.push_back({});
+    addr = &addresses.back();
+    address(*addr);
+  }
+  if (addresses.size() == 1
+      && addr->offset == 0 && !addr->bufname.has_value()
+      && std::holds_alternative<AddressPromise::None>(addr->base))
+    addresses.pop_back();
+}
+} // namespace bed::internal::parser
diff --git a/src/internal/parser/address_promise.cc b/src/internal/parser/address_promise.cc
index 96927bb..1d5942a 100644
--- a/src/internal/parser/address_promise.cc
+++ b/src/internal/parser/address_promise.cc
@@ -6,13 +6,16 @@ namespace bed::internal::parser {
 buffer::Line AddressPromise::resolve(BEd &ctx) {
   buffer::Line result = std::visit(
     [&](auto const &addr) -> buffer::Line {
-      if (!bufname.has_value())
+      if (!bufname.has_value() || bufname->empty())
         throw ed_error("Buffer name can't be empty.");
       buffer::Line line = {*bufname, 0};
       auto &buf = ctx.buffer(line.buffername);
       using T = std::decay_t<decltype(addr)>;
       if constexpr (std::is_same_v<T, None>) {
-        throw ed_error("no address");
+        if (line.buffername == ctx.current().buffername)
+          line.number = ctx.current().number;
+        else
+          line.number = buf.lines();
       } else if constexpr (std::is_same_v<T, Current>) {
         if (line.buffername == ctx.current().buffername)
           line.number = ctx.current().number;
@@ -133,15 +136,18 @@ std::optional<buffer::Line> AddressPromise::get_line(BEd &ctx, std::vector<Addre
       prev_set = true;
     } else {
       if (std::holds_alternative<None>(curr.base)) {
-        if (!prev_set)
-          return std::nullopt;
-        if (prev_given) {
-          curr.base = prev.base;
-          curr.offset = prev.offset;
-        } else {
-          curr.base = Last();
-          curr.offset = 0;
+        if (prev_set) {
+          if (prev_given) {
+            curr.base = prev.base;
+            curr.offset = prev.offset;
+          } else {
+            curr.base = Last();
+            curr.offset = 0;
+          }
         }
+      } else if (std::holds_alternative<LastRange>(curr.base)) {
+        curr.bufname = ctx.prev.buffername;
+        curr.base = Number(ctx.prev.end);
       }
       return curr.resolve(ctx);
     }
@@ -193,16 +199,18 @@ std::optional<buffer::Range> AddressPromise::get_range(BEd &ctx, std::vector<Add
       prev_set = true;
     } else {
       if (std::holds_alternative<None>(curr.base)) {
-        if (!prev_set)
-          return std::nullopt;
-        if (prev_given) {
-          curr.base = prev.base;
-          curr.offset = prev.offset;
-        } else {
-          curr.base = Last();
-          curr.offset = 0;
+        if (prev_set) {
+          if (prev_given) {
+            curr.base = prev.base;
+            curr.offset = prev.offset;
+          } else {
+            curr.base = Last();
+            curr.offset = 0;
+          }
+          return buffer::Range(prev.resolve(ctx), curr.resolve(ctx));
         }
-        return buffer::Range(prev.resolve(ctx), curr.resolve(ctx));
+      } else if (std::holds_alternative<LastRange>(curr.base)) {
+        return ctx.prev;
       }
       if (prev_given)
         return buffer::Range(prev.resolve(ctx), curr.resolve(ctx));
diff --git a/src/internal/parser/operation.cc b/src/internal/parser/operation.cc
new file mode 100644
index 0000000..c90d65e
--- /dev/null
+++ b/src/internal/parser/operation.cc
@@ -0,0 +1,205 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed::internal::parser {
+void Parser::operation() {
+  if (peek() == '\0') {
+    command->function = &bed.no_op;
+    return;
+  }
+  uint64_t len = bed.functions.longest_match(peek_str());
+  if (len == 0)
+    throw ed_error("Function not found.");
+  functions::Function *function = bed.functions.get_ptr(peek_str(len));
+  advance(len);
+  command->function = function;
+  char suffix = '\0';
+  switch (command->function->argument_kind) {
+  case functions::Function::ArgumentKind::None:
+    break;
+  case functions::Function::ArgumentKind::Number:
+    skip_ws();
+    command->argument = offset();
+    break;
+  case functions::Function::ArgumentKind::Mark:
+    if (('a' <= peek() && peek() <= 'z')
+        || ('A' <= peek() && peek() <= 'Z'))
+      command->argument = peek();
+    else
+      throw ed_error("Valid mark needed.");
+    advance();
+    break;
+  case functions::Function::ArgumentKind::Any:
+    command->argument = std::string(peek_str());
+    advance(peek_str().size());
+    break;
+  case functions::Function::ArgumentKind::Global: {
+    char delim;
+    std::string val;
+    switch (peek()) {
+    case '\0':
+      throw ed_error("Command needs a delimited value.");
+    case '{': {
+      advance();
+      delim = '}';
+      uint16_t j = 0;
+      while (peek(j) != '}' && peek(j) != '\0') {
+        if (peek(j) == '\\')
+          j++;
+        j++;
+      }
+      switch (peek(j)) {
+      case '\0':
+        throw ed_error("Unterminated {");
+      case '}':
+        val = peek_str(j);
+        break;
+      }
+      advance(j + 1);
+    } break;
+    case '<': {
+      advance();
+      delim = '<';
+      uint16_t j = 0;
+      while (peek(j) != '>' || peek(j) != '\0') {
+        if (peek(j) == '\\')
+          j++;
+        j++;
+      }
+      switch (peek(j)) {
+      case '\0':
+        throw ed_error("Unterminated <");
+      case '>':
+        val = peek_str(j);
+        break;
+      }
+      advance(j + 1);
+    } break;
+    case '^':
+    case '~':
+      advance();
+      delim = '^';
+      break;
+    default:
+      delim = peek();
+      advance();
+      uint64_t j = 0;
+      while (true) {
+        if (peek(j) == '\0')
+          break;
+        if (peek(j) == delim)
+          break;
+        else if (peek(j) == '\\')
+          j += 2;
+        else if (peek(j) == '[')
+          while (peek(j) != '\0' && cmd[i] != ']')
+            j++;
+        else
+          j++;
+      }
+      val = peek_str(j);
+      advance(j + 1);
+    }
+    command->argument = functions::Function::GlobalArg(delim, std::move(val));
+  } break;
+  case functions::Function::ArgumentKind::File:
+    skip_ws();
+    switch (peek()) {
+    case '!':
+      advance();
+      command->argument = functions::Function::ShellArg(std::string(peek_str()));
+      advance(peek_str().size());
+      break;
+    case '\0':
+      command->argument = std::monostate();
+      break;
+    default:
+      command->argument = std::filesystem::path(peek_str());
+      advance(peek_str().size());
+      break;
+    }
+    break;
+  case functions::Function::ArgumentKind::Line:
+    command->argument = buffer::Line();
+    addresses(command->argument_addresses);
+    break;
+  case functions::Function::ArgumentKind::Range:
+    command->argument = buffer::Range();
+    addresses(command->argument_addresses);
+    break;
+  case functions::Function::ArgumentKind::Regex: {
+    char delim = peek();
+    if (delim == '\0')
+      throw ed_error("regex expected");
+    advance();
+    uint64_t j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        throw ed_error("Unterminated regex");
+      if (peek(j) == delim)
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && cmd[i] != ']')
+          j++;
+      else
+        j++;
+    }
+    std::string expression(peek_str(j));
+    advance(j + 1);
+    j = 0;
+    while (true) {
+      if (peek(j) == '\0')
+        break;
+      if (peek(j) == delim)
+        break;
+      else if (peek(j) == '\\')
+        j += 2;
+      else if (peek(j) == '[')
+        while (peek(j) != '\0' && cmd[i] != ']')
+          j++;
+      else
+        j++;
+    }
+    std::string replacement;
+    if (peek(j) != '\0') {
+      replacement = peek_str(j);
+      advance(j + 1);
+    }
+    std::string options;
+    if (peek() != '\0') {
+      options = std::string(peek_str());
+      advance(peek_str().size());
+    }
+    std::erase_if(options, [&](char c) {
+      if (bed.suffixes[c - 'a'].has_value()) {
+        suffix = c;
+        return true;
+      }
+      return false;
+    });
+    command->argument = functions::Function::RegexArg(expression, replacement, options);
+  } break;
+  case functions::Function::ArgumentKind::Ruby:
+    command->argument = functions::Function::RubyArg(std::string(peek_str()));
+    advance(peek_str().size());
+    break;
+  case functions::Function::ArgumentKind::Shell:
+    command->argument = functions::Function::ShellArg(std::string(peek_str()));
+    advance(peek_str().size());
+    break;
+  }
+  if (!suffix) {
+    suffix = peek();
+    advance();
+  }
+  if (suffix) {
+    auto &s = bed.suffixes[suffix - 'a'];
+    if (s.has_value())
+      command->suffix = &s.value();
+    else
+      throw ed_error("Invalid suffix.");
+  }
+}
+} // namespace bed::internal::parser
diff --git a/src/internal/parser/parser.cc b/src/internal/parser/parser.cc
index 8284af3..3e6fee0 100644
--- a/src/internal/parser/parser.cc
+++ b/src/internal/parser/parser.cc
@@ -19,455 +19,6 @@ void Parser::skip_ws() {
     advance();
 }
 
-void Parser::locator(AddressPromise &addr) {
-  addr.base = AddressPromise::None{};
-  switch (peek()) {
-  case '.':
-    advance();
-    addr.base = AddressPromise::Current{};
-    break;
-  case '$':
-    advance();
-    addr.base = AddressPromise::Last{};
-    break;
-  case '%':
-    advance();
-    addr.base = AddressPromise::LastRange{};
-    break;
-  case '[':
-    advance();
-    addr.base = AddressPromise::Block{Direction::Backward};
-    break;
-  case ']':
-    advance();
-    addr.base = AddressPromise::Block{Direction::Forward};
-    break;
-  case '^':
-    advance();
-    addr.base = AddressPromise::Diagnostic{Direction::Backward};
-    break;
-  case '~':
-    advance();
-    addr.base = AddressPromise::Diagnostic{Direction::Forward};
-    break;
-  case '\'':
-    advance();
-    if (('a' <= peek() && peek() <= 'z')
-        || ('A' <= peek() && peek() <= 'Z'))
-      addr.base = AddressPromise::Mark{peek()};
-    else
-      throw ed_error("Valid mark needed after \'");
-    advance();
-    break;
-  case '{': {
-    advance();
-    uint16_t j = 0;
-    std::string func;
-    std::string arg;
-    while (peek(j) != '}') {
-      if (peek(j) == '\0')
-        throw ed_error("Scripted address not terminated");
-      if (peek(j) == '\\')
-        ++j;
-      if (peek(j) == ':') {
-        func = peek_str(j);
-        advance(j + 1);
-        j = 0;
-        continue;
-      }
-      ++j;
-    }
-    if (func.size())
-      arg = peek_str(j);
-    else
-      func = peek_str(j);
-    addr.base = AddressPromise::Scripted{std::move(func), std::move(arg)};
-    advance(j + 1);
-  } break;
-  case '/': {
-    advance();
-    uint64_t j = 0;
-    while (true) {
-      if (peek(j) == '\0')
-        break;
-      if (peek(j) == '/')
-        break;
-      else if (peek(j) == '\\')
-        j += 2;
-      else if (peek(j) == '[')
-        while (peek(j) != '\0' && cmd[i] != ']')
-          j++;
-      else
-        j++;
-    }
-    addr.base = AddressPromise::Regex(
-      Direction::Forward,
-      std::string(peek_str(j))
-    );
-    advance(j + 1);
-  } break;
-  case '?': {
-    advance();
-    uint16_t j = 0;
-    while (true) {
-      if (peek(j) == '\0')
-        break;
-      if (peek(j) == '?')
-        break;
-      else if (peek(j) == '\\')
-        j += 2;
-      else if (peek(j) == '[')
-        while (peek(j) != '\0' && cmd[i] != ']')
-          j++;
-      else
-        j++;
-    }
-    addr.base = AddressPromise::Regex(
-      Direction::Backward,
-      std::string(peek_str(j))
-    );
-    advance(j + 1);
-  } break;
-  case '<': {
-    advance();
-    uint16_t j = 0;
-    while (peek(j) != '>'
-           && peek(j) != '<'
-           && peek(j) != '\0')
-      j++;
-    switch (peek(j)) {
-    case '\0':
-    case '>':
-      addr.base = AddressPromise::SymbolDefinition{
-        std::string(peek_str(j))
-      };
-      break;
-    case '<':
-      addr.base = AddressPromise::SymbolReference{
-        Direction::Backward,
-        std::string(peek_str(j))
-      };
-      break;
-    }
-    advance(j + 1);
-  } break;
-  case '>': {
-    advance();
-    uint16_t j = 0;
-    while (peek(j) != '>' && peek(j) != '\0')
-      j++;
-    switch (peek(j)) {
-    case '\0':
-      throw ed_error("Unterminated symbol reference addressing.");
-    case '>':
-      addr.base = AddressPromise::SymbolReference{
-        Direction::Forward,
-        std::string(peek_str(j))
-      };
-      break;
-    }
-    advance(j + 1);
-  } break;
-  case '+': {
-    advance();
-    addr.base = AddressPromise::Current{};
-    uint16_t j = 0;
-    uint64_t num = 0;
-    while ('0' <= peek(j) && peek(j) <= '9') {
-      num = num * 10 + (peek(j) - '0');
-      j++;
-    }
-    if (j == 0)
-      num = 1;
-    advance(j);
-    addr.offset += num;
-  } break;
-  case '-': {
-    advance();
-    addr.base = AddressPromise::Current{};
-    uint16_t j = 0;
-    uint64_t num = 0;
-    while ('0' <= peek(j) && peek(j) <= '9') {
-      num = num * 10 + (peek(j) - '0');
-      j++;
-    }
-    if (j == 0)
-      num = 1;
-    advance(j);
-    addr.offset -= num;
-  } break;
-  default:
-    if ('0' <= peek() && peek() <= '9') {
-      uint64_t num = 0;
-      while ('0' <= peek() && peek() <= '9') {
-        num = num * 10 + (peek() - '0');
-        advance();
-      }
-      addr.base = AddressPromise::Number{num};
-    }
-  }
-}
-
-int64_t Parser::offset() {
-  int64_t offset = 0;
-  while (peek() == '+' || peek() == '-'
-         || ('0' <= peek() && peek() <= '9')) {
-    bool positive = peek() != '-';
-    if (peek() == '+' || peek() == '-')
-      advance();
-    uint16_t j = 0;
-    int64_t num = 0;
-    while ('0' <= peek(j) && peek(j) <= '9')
-      num = num * 10 + (peek(j++) - '0');
-    if (j == 0)
-      num = 1;
-    advance(j);
-    offset += positive ? num : -num;
-    skip_ws();
-  }
-  skip_ws();
-  return offset;
-}
-
-void Parser::address(AddressPromise &addr) {
-  if (peek() == ':') {
-    advance();
-    uint16_t j = 0;
-    while (peek(j) != ':' && peek(j) != '\0')
-      j++;
-    addr.bufname = peek_str(j);
-    advance(j);
-    if (peek() == ':')
-      advance();
-  }
-  skip_ws();
-  if (peek() == '\0')
-    return;
-  locator(addr);
-  skip_ws();
-  addr.offset += offset();
-}
-
-void Parser::addresses(std::vector<AddressPromise> &addresses) {
-  skip_ws();
-  addresses.push_back({});
-  auto *addr = &addresses.back();
-  address(*addr);
-  while (peek() == ',' || peek() == ';') {
-    addr->jumping = peek() == ';';
-    advance();
-    skip_ws();
-    addresses.push_back({});
-    addr = &addresses.back();
-    address(*addr);
-  }
-  if (addresses.size() == 1
-      && addr->offset == 0 && addr->bufname.has_value()
-      && std::holds_alternative<AddressPromise::None>(addr->base))
-    addresses.pop_back();
-}
-
-void Parser::operation() {
-  if (peek() == '\0') {
-    command->function = &bed.no_op;
-    return;
-  }
-  uint64_t len = bed.functions.longest_match(peek_str());
-  if (len == 0)
-    throw ed_error("Function not found.");
-  functions::Function *function = bed.functions.get_ptr(peek_str(len));
-  advance(len);
-  command->function = function;
-  char suffix = '\0';
-  switch (command->function->argument_kind) {
-  case functions::Function::ArgumentKind::None:
-    break;
-  case functions::Function::ArgumentKind::Number:
-    skip_ws();
-    command->argument = offset();
-    break;
-  case functions::Function::ArgumentKind::Mark:
-    if (('a' <= peek() && peek() <= 'z')
-        || ('A' <= peek() && peek() <= 'Z'))
-      command->argument = peek();
-    else
-      throw ed_error("Valid mark needed.");
-    advance();
-    break;
-  case functions::Function::ArgumentKind::Any:
-    command->argument = std::string(peek_str());
-    advance(peek_str().size());
-    break;
-  case functions::Function::ArgumentKind::Global: {
-    char delim;
-    std::string val;
-    switch (peek()) {
-    case '\0':
-      throw ed_error("Command needs a delimited value.");
-    case '{': {
-      advance();
-      delim = '}';
-      uint16_t j = 0;
-      while (peek(j) != '}' && peek(j) != '\0') {
-        if (peek(j) == '\\')
-          j++;
-        j++;
-      }
-      switch (peek(j)) {
-      case '\0':
-        throw ed_error("Unterminated {");
-      case '}':
-        val = peek_str(j);
-        break;
-      }
-      advance(j + 1);
-    } break;
-    case '<': {
-      advance();
-      delim = '<';
-      uint16_t j = 0;
-      while (peek(j) != '>' || peek(j) != '\0') {
-        if (peek(j) == '\\')
-          j++;
-        j++;
-      }
-      switch (peek(j)) {
-      case '\0':
-        throw ed_error("Unterminated <");
-      case '>':
-        val = peek_str(j);
-        break;
-      }
-      advance(j + 1);
-    } break;
-    case '^':
-    case '~':
-      advance();
-      delim = '^';
-      break;
-    default:
-      delim = peek();
-      advance();
-      uint64_t j = 0;
-      while (true) {
-        if (peek(j) == '\0')
-          break;
-        if (peek(j) == delim)
-          break;
-        else if (peek(j) == '\\')
-          j += 2;
-        else if (peek(j) == '[')
-          while (peek(j) != '\0' && cmd[i] != ']')
-            j++;
-        else
-          j++;
-      }
-      val = peek_str(j);
-      advance(j + 1);
-    }
-    command->argument = functions::Function::GlobalArg(delim, std::move(val));
-  } break;
-  case functions::Function::ArgumentKind::File:
-    skip_ws();
-    switch (peek()) {
-    case '!':
-      advance();
-      command->argument = functions::Function::ShellArg(std::string(peek_str()));
-      advance(peek_str().size());
-      break;
-    case '\0':
-      command->argument = std::monostate();
-      break;
-    default:
-      command->argument = std::filesystem::path(peek_str());
-      advance(peek_str().size());
-      break;
-    }
-    break;
-  case functions::Function::ArgumentKind::Line:
-    command->argument = buffer::Line();
-    addresses(command->argument_addresses);
-    break;
-  case functions::Function::ArgumentKind::Range:
-    command->argument = buffer::Range();
-    addresses(command->argument_addresses);
-    break;
-  case functions::Function::ArgumentKind::Regex: {
-    char delim = peek();
-    if (delim == '\0')
-      throw ed_error("regex expected");
-    advance();
-    uint64_t j = 0;
-    while (true) {
-      if (peek(j) == '\0')
-        throw ed_error("Unterminated regex");
-      if (peek(j) == delim)
-        break;
-      else if (peek(j) == '\\')
-        j += 2;
-      else if (peek(j) == '[')
-        while (peek(j) != '\0' && cmd[i] != ']')
-          j++;
-      else
-        j++;
-    }
-    std::string expression(peek_str(j));
-    advance(j + 1);
-    j = 0;
-    while (true) {
-      if (peek(j) == '\0')
-        break;
-      if (peek(j) == delim)
-        break;
-      else if (peek(j) == '\\')
-        j += 2;
-      else if (peek(j) == '[')
-        while (peek(j) != '\0' && cmd[i] != ']')
-          j++;
-      else
-        j++;
-    }
-    std::string replacement;
-    if (peek(j) != '\0') {
-      replacement = peek_str(j);
-      advance(j + 1);
-    }
-    std::string options;
-    if (peek() != '\0') {
-      options = std::string(peek_str());
-      advance(peek_str().size());
-    }
-    std::erase_if(options, [&](char c) {
-      if (bed.suffixes[c - 'a'].has_value()) {
-        suffix = c;
-        return true;
-      }
-      return false;
-    });
-    command->argument = functions::Function::RegexArg(expression, replacement, options);
-  } break;
-  case functions::Function::ArgumentKind::Ruby:
-    command->argument = functions::Function::RubyArg(std::string(peek_str()));
-    advance(peek_str().size());
-    break;
-  case functions::Function::ArgumentKind::Shell:
-    command->argument = functions::Function::ShellArg(std::string(peek_str()));
-    advance(peek_str().size());
-    break;
-  }
-  if (!suffix) {
-    suffix = peek();
-    advance();
-  }
-  if (suffix) {
-    auto &s = bed.suffixes[suffix - 'a'];
-    if (s.has_value())
-      command->suffix = &s.value();
-    else
-      throw ed_error("Invalid suffix.");
-  }
-}
-
 void Parser::parse() {
   skip_ws();
   if (peek() == '@') {
@@ -486,14 +37,14 @@ void Parser::parse() {
 
 Parser::Parser(
   std::string_view cmd, BEd &bed, Command *command,
-  std::vector<io::Token> *tokens, CompletionContext *completion
+  std::vector<ui::Token> *tokens, CompletionContext *completion
 ) : bed(bed), cmd(cmd), command(command), tokens(tokens), completion(completion) {
   i = 0;
 }
 
 Command Parser::get_command(std::string_view cmd, BEd &bed) {
   Command c;
-  std::vector<io::Token> tokens;
+  std::vector<ui::Token> tokens;
   CompletionContext completion;
   Parser p(cmd, bed, &c, &tokens, &completion);
   p.parse();
@@ -502,7 +53,7 @@ Command Parser::get_command(std::string_view cmd, BEd &bed) {
 
 std::vector<AddressPromise> Parser::get_addresses(std::string_view cmd, BEd &bed) {
   std::vector<AddressPromise> result;
-  std::vector<io::Token> tokens;
+  std::vector<ui::Token> tokens;
   CompletionContext completion;
   Parser p(cmd, bed, nullptr, &tokens, &completion);
   p.addresses(result);
diff --git a/src/internal/syntax/parser.cc b/src/internal/syntax/parser.cc
index 0e09672..18dbfa3 100644
--- a/src/internal/syntax/parser.cc
+++ b/src/internal/syntax/parser.cc
@@ -1,42 +1,6 @@
 #include "internal/syntax/parser.h"
 
 namespace bed::internal::syntax {
-void dump_events(ParseState *root) {
-  if (!root)
-    return;
-  uint64_t offset = 0;
-  TreeCursor c(root, 0, &offset);
-  uint64_t line_offset = 0;
-  int depth = 0;
-  while (c.leaf) {
-    auto *leaf = c.leaf;
-    for (uint32_t i = 0; i < leaf->n; ++i) {
-      uint32_t block = leaf->blocks[i];
-      uint32_t pos = block & ParseStateLeaf::LINE_MASK;
-      bool closing = block & ParseStateLeaf::IS_CLOSING;
-      if (closing) {
-        if (depth > 0)
-          --depth;
-        else
-          std::cout << "!! UNMATCHED CLOSE !! ";
-      }
-      std::cout << std::string(static_cast<size_t>(depth) * 2, ' ')
-                << (closing ? "}" : "{")
-                << " line " << (line_offset + pos)
-                << '\n';
-      if (!closing)
-        ++depth;
-    }
-    line_offset += leaf->lines();
-    c.next();
-  }
-  if (depth != 0) {
-    std::cout << "!! UNBALANCED: depth = "
-              << depth
-              << " !!\n";
-  }
-}
-
 static void destroy_tree(ParseState *node, Language &lang) {
   if (!node)
     return;
diff --git a/src/internal/ui/command/command.cc b/src/internal/ui/command/command.cc
new file mode 100644
index 0000000..1787020
--- /dev/null
+++ b/src/internal/ui/command/command.cc
@@ -0,0 +1,158 @@
+#include "internal/ui/command.h"
+#include "bed.h"
+
+namespace bed::internal::ui {
+/*template <typename F>
+static void for_each_cluster(std::string_view s, F &&f) {
+  unicode_width_state_t state;
+  unicode_width_init(&state);
+  size_t i = 0;
+  while (i < s.size()) {
+    unsigned char c = static_cast<unsigned char>(s[i]);
+    size_t bytes = 1;
+    int width = 0;
+    if (c < 128) {
+      width = unicode_width_process(&state, c);
+    } else {
+      uint_least32_t cp;
+      size_t decoded = grapheme_decode_utf8(s.data() + i, s.size() - i, &cp);
+      bytes = decoded > 0 ? decoded : 1;
+      width = unicode_width_process(&state, cp);
+    }
+    if (width < 0)
+      width = 0;
+    f(i, bytes, width);
+    i += bytes;
+  }
+}
+
+static int display_width(std::string_view s) {
+  int w = 0;
+  for_each_cluster(s, [&](size_t, size_t, int cw) { w += cw; });
+  return w;
+}
+
+static uint16_t count_clusters(std::string_view s) {
+  uint16_t n = 0;
+  for_each_cluster(s, [&](size_t, size_t, int) { ++n; });
+  return n;
+}
+
+static std::vector<uint16_t> wrap_offsets(std::string_view line, uint16_t avail) {
+  std::vector<uint16_t> offsets{0};
+  int col = 0;
+  for_each_cluster(line, [&](uint16_t i, uint16_t, int w) {
+    if (col + w > avail && col > 0) {
+      offsets.push_back(i);
+      col = 0;
+    }
+    col += w;
+  });
+  return offsets;
+}
+
+// The word under/before `byte_pos`, split on plain ASCII spaces. Used to
+// pick what prefix to hand the suggestion trie.
+// TODO: change to use libgrapheme word break here.
+static std::string current_word(const std::string &line, size_t byte_pos) {
+  size_t start = (byte_pos == 0) ? std::string::npos : line.rfind(' ', byte_pos - 1);
+  start = (start == std::string::npos) ? 0 : start + 1;
+  if (byte_pos < start)
+    byte_pos = start;
+  return line.substr(start, byte_pos - start);
+}*/
+
+CommandIO::CommandIO(BEd &bed, io::IO &io) : bed(bed), io(io) {
+  if (bed.prompt_mode)
+    prompt = bed.prompt(bed);
+  cursor = 0;
+}
+
+std::pair<std::string, bool> CommandIO::run() {
+  auto [row, col] = io.cursor_position();
+  auto [rows, cols] = io.terminal_size();
+  if (row > rows)
+    throw fatal_error("Invalid cursor position.", 1);
+  start = row;
+  height = rows - row + 1;
+  term_width = cols;
+  term_height = rows;
+  redraw();
+
+  // main loop.
+  io::KeyEvent res;
+  bool running = true;
+  while (running) {
+    res = io.read_key();
+    switch (res.type) {
+    case io::KeyEvent::KeyType::EOF_:
+      running = false;
+      break;
+    case io::KeyEvent::KeyType::MOUSE:
+    case io::KeyEvent::KeyType::RESIZE:
+      break;
+    case io::KeyEvent::KeyType::CHAR:
+      switch (res.modifier) {
+      case io::KeyEvent::Modifier::SHIFT:
+      case io::KeyEvent::Modifier::ALT:
+      case io::KeyEvent::Modifier::CTRL_ALT:
+      case io::KeyEvent::Modifier::CTRL:
+        break;
+      case io::KeyEvent::Modifier::NONE:
+        if (res.text[0] == '\b' || res.text[0] == 0x7f) {
+          if (cursor > 0)
+            cmd.erase(--cursor, 1);
+        } else if (res.text[0] == '\n') {
+          running = false;
+        } else {
+          cmd.insert(cursor++, res.text);
+        }
+        break;
+      }
+      break;
+    case io::KeyEvent::KeyType::PASTE:
+      cmd.insert(cursor, res.text);
+      cursor += res.text.size();
+      break;
+    case io::KeyEvent::KeyType::SPECIAL:
+      switch (res.special_key) {
+      case io::KeyEvent::SpecialKey::UNKNOWN:
+      case io::KeyEvent::SpecialKey::UP:
+      case io::KeyEvent::SpecialKey::DOWN:
+        break;
+      case io::KeyEvent::SpecialKey::RIGHT:
+        if (cursor < cmd.size())
+          cursor++;
+        break;
+      case io::KeyEvent::SpecialKey::LEFT:
+        if (cursor > 0)
+          cursor--;
+        break;
+      case io::KeyEvent::SpecialKey::DELETE:
+        if (cursor < cmd.size())
+          cmd.erase(cursor, 1);
+        break;
+      }
+      break;
+    }
+    redraw();
+  }
+
+  for (uint16_t i = 1; i < height; ++i) {
+    io.move_cursor(start + i, 1);
+    io.write("\x1b[2K", 4);
+  }
+  io.move_cursor(start, 1);
+  io.write("\n", 1);
+  return {cmd, false};
+}
+
+void CommandIO::redraw() {
+  io.move_cursor(start, 1);
+  io.write("\x1b[2K", 4);
+  io.move_cursor(start, 1);
+  io.write(prompt);
+  io.write(cmd);
+  io.move_cursor(start, prompt.size() + cursor + 1);
+}
+} // namespace bed::internal::ui
diff --git a/src/internal/vase/regex/api.cc b/src/internal/vase/regex/api.cc
index db45280..c6a441e 100644
--- a/src/internal/vase/regex/api.cc
+++ b/src/internal/vase/regex/api.cc
@@ -80,20 +80,15 @@ Shard *substitute(
     (end + 1 == line_count)
       ? root->length
       : offset_of(root, end + 1);
-
   std::vector<RegexMatch> matches = _regex_search(root, pattern, start_offset, end_offset, options);
   if (matches.empty())
     return root;
-
   std::vector<ReplacePart> replace_parts = parse_replace(ap, replace);
-
   std::vector<Shard *> pieces;
   pieces.reserve(matches.size() * 2 + 1);
-
   Shard *remaining = root;
   Shard::retain(remaining);
   uint64_t cursor = 0;
-
   for (const RegexMatch &match : matches) {
     uint64_t gap = match.start - cursor;
     if (gap > 0) {
@@ -102,11 +97,9 @@ Shard *substitute(
       pieces.push_back(keep);
       remaining = rest;
     }
-
     auto [dropped, rest2] = Shard::split(remaining, match.end - match.start);
     Shard::release(remaining);
     remaining = rest2;
-
     for (size_t i = 0; i < replace_parts.size(); ++i) {
       const ReplacePart &part = replace_parts[i];
       switch (part.type) {
@@ -141,11 +134,9 @@ Shard *substitute(
     cursor = match.end;
   }
   pieces.push_back(remaining);
-
   for (auto &part : replace_parts)
     if (part.type == ReplacePart::PartType::Constant)
       Shard::release(std::get<Shard *>(part.value));
-
   std::vector<Shard *> compact;
   compact.reserve(pieces.size());
   for (Shard *p : pieces) {
@@ -154,7 +145,6 @@ Shard *substitute(
     else if (p)
       Shard::release(p);
   }
-
   Shard *new_root = compact.empty() ? nullptr : Shard::build(compact.data(), 0, compact.size());
   Shard::release(root);
   return new_root;
diff --git a/src/internal/vase/shard.cc b/src/internal/vase/shard.cc
index 3d15bb9..e0c95d0 100644
--- a/src/internal/vase/shard.cc
+++ b/src/internal/vase/shard.cc
@@ -1,3 +1,4 @@
+#include "internal/io/io.h"
 #include "internal/vase/vase.h"
 
 namespace bed::internal::vase {
@@ -192,10 +193,10 @@ Shard *Shard::append(Shard *root, Shard *leaf) {
 Shard *Shard::build(Shard **pieces, uint64_t lo, uint64_t hi) {
   if (hi - lo == 1)
     return pieces[lo];
-  size_t mid = lo + (hi - lo) / 2;
+  uint64_t mid = lo + (hi - lo) / 2;
   Shard *left = build(pieces, lo, mid);
   Shard *right = build(pieces, mid, hi);
-  Shard *node = new Branch(left, right);
+  Shard *node = Shard::concat(left, right);
   Shard::release(left);
   Shard::release(right);
   return node;
@@ -208,9 +209,11 @@ Shard *Shard::from_command(const char *cmd, bool posix_ending) {
     delete o;
     return nullptr;
   }
+  io::IO::cleanup();
   FILE *pipe = popen(cmd, "r");
   if (!pipe) {
     delete o;
+    io::IO::enable_raw();
     return nullptr;
   }
   std::vector<Shard *> pieces;
@@ -245,6 +248,7 @@ Shard *Shard::from_command(const char *cmd, bool posix_ending) {
       if (!write_all(dest_fd, buf, buf_cursor)) {
         pclose(pipe);
         delete o;
+        io::IO::enable_raw();
         return nullptr;
       }
       pieces.push_back(new Petal(buf_cursor, lines, o, pos));
@@ -254,20 +258,24 @@ Shard *Shard::from_command(const char *cmd, bool posix_ending) {
       break;
     if (ferror(pipe)) {
       delete o;
+      io::IO::enable_raw();
       return nullptr;
     }
   }
   int status = pclose(pipe);
   if (status == -1) {
     delete o;
+    io::IO::enable_raw();
     return nullptr;
   }
   if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
     delete o;
+    io::IO::enable_raw();
     return nullptr;
   }
   if (pieces.empty()) {
     delete o;
+    io::IO::enable_raw();
     return nullptr;
   }
   if (posix_ending) {
@@ -287,6 +295,7 @@ Shard *Shard::from_command(const char *cmd, bool posix_ending) {
     }
   }
   o->initialize();
+  io::IO::enable_raw();
   if (pieces.size() == 1)
     return pieces[0];
   return build(pieces.data(), 0, pieces.size());
@@ -421,54 +430,4 @@ Shard *Shard::from_string(const char *data, uint64_t len, bool posix_ending) {
     return pieces[0];
   return build(pieces.data(), 0, pieces.size());
 }
-
-void Shard::dump(Shard *node, int depth) {
-  if (!node) {
-    std::cout << std::string(depth * 2, ' ') << "<null>\n";
-    return;
-  }
-  std::string indent(depth * 2, ' ');
-  std::cout << indent
-            << "Shard@" << node
-            << " kind=";
-  switch (node->kind) {
-  case Shard::Kind::Branch:
-    std::cout << "Branch";
-    break;
-  case Shard::Kind::Petal:
-    std::cout << "Petal";
-    break;
-  }
-  std::cout
-    << " height=" << unsigned(node->height)
-    << " length=" << node->length
-    << " lines=" << node->lines
-    << " refs=" << node->refs.load()
-    << "\n";
-  if (node->kind == Shard::Kind::Branch) {
-    auto *branch = (Branch *)node;
-    std::cout << indent << "  left:\n";
-    dump(branch->left, depth + 2);
-    std::cout << indent << "  right:\n";
-    dump(branch->right, depth + 2);
-  } else {
-    auto *petal = static_cast<Petal *>(node);
-    constexpr auto clean = [](const std::string &text) {
-      std::string result = text;
-      size_t pos = 0;
-      while ((pos = result.find('\n', pos)) != std::string::npos) {
-        result.replace(pos, 1, "\\n");
-        pos += 2;
-      }
-      return result;
-    };
-    std::cout
-      << indent << "  source=" << petal->source
-      << " pos=" << petal->pos
-      << " length=" << petal->length
-      << " lines=" << petal->lines
-      << " text=\"" << clean(std::string(petal->source->read(petal->pos), petal->length))
-      << "\"\n";
-  }
-}
 } // namespace bed::internal::vase
diff --git a/src/internal/vase/vase.cc b/src/internal/vase/vase.cc
index 8f1e2c1..4ed9272 100644
--- a/src/internal/vase/vase.cc
+++ b/src/internal/vase/vase.cc
@@ -222,6 +222,38 @@ Shard *erase(Shard *root, uint64_t start, uint64_t end) {
   return new_root;
 }
 
+Shard *join(Shard *root, uint64_t start, uint64_t end) {
+  if (!start || !end)
+    throw ed_error("Invalid range.");
+  start--;
+  end--;
+  if (!root)
+    throw ed_error("line range out of bounds");
+  uint64_t line_count = root->lines + 1;
+  if (start >= end || end >= line_count)
+    throw ed_error("line range out of bounds");
+
+  uint64_t offset = offset_of(root, start);
+  std::vector<Shard *> pieces;
+  pieces.reserve(end - start + 3);
+  auto [a, b] = Shard::split(root, offset);
+  pieces.push_back(a);
+  for (uint64_t line = start; line < end; line++) {
+    uint64_t nl_pos = offset_of(b, 1) - 1;
+    auto [content, rest] = Shard::split(b, nl_pos);
+    Shard::release(b);
+    auto [nl, next_b] = Shard::split(rest, 1);
+    Shard::release(rest);
+    Shard::release(nl);
+    pieces.push_back(content);
+    b = next_b;
+  }
+  pieces.push_back(b);
+  Shard *joined = Shard::build(pieces.data(), 0, pieces.size());
+  Shard::release(root);
+  return joined;
+}
+
 Shard *copy(Shard *root, uint64_t start, uint64_t end) {
   if (!start || !end)
     throw ed_error("Invalid range.");