diff --git a/include/commands/ed/ed.h b/include/commands/ed/ed.h
index 03ba39f..d41b383 100644
--- a/include/commands/ed/ed.h
+++ b/include/commands/ed/ed.h
@@ -4,6 +4,84 @@
 #include "pch.h"
 
 namespace crib::commands::ed {
+struct ed_error : std::runtime_error {
+  ed_error(const char *msg) : std::runtime_error(msg) {}
+};
+
+struct Command {
+  enum struct Type : uint8_t {
+    Invalid,
+    Quit,
+    ForceQuit,
+    PromptToggle,
+    HelpToggle,
+    Help,
+    Print,
+    Number,
+    Append,
+    Change,
+    Delete,
+    Write,
+    Dump,
+    None
+  } type;
+
+  struct Address {
+    enum struct Type : uint8_t {
+      None,
+      Current,
+      Last,
+      Number,
+      Mark,
+      SearchForward,
+      SearchBackward
+    } type;
+    int64_t number = 0;
+    std::string regex = "";
+    int64_t offset = 0;
+    char mark = '\0';
+  };
+
+  Address start{};
+  Address end{};
+  static constexpr uint8_t SEMICOLON = 0b01;
+  static constexpr uint8_t RANGE = 0b10;
+  uint8_t address_flags = 0;
+  char suffix = '\0';
+  std::string argument;
+};
+
+struct Ed {
+  crib::internal::vase::Vase vase;
+  uint64_t line = 0;
+  bool modified = false;
+  bool quitting = false;
+  uint64_t marks[26]{0};
+  std::string last_regex = "";
+  bool help_mode = false;
+  bool suppress_mode = false;
+  bool prompt_mode = false;
+  std::string prompt = "*";
+  std::string last_message = "";
+
+  Ed(std::filesystem::path file, bool suppress_mode, std::string prompt_)
+      : vase(file, "/tmp"), suppress_mode(suppress_mode), prompt(prompt_) {
+    if (prompt == "")
+      prompt = "*";
+    else
+      prompt_mode = true;
+    line = vase.lines();
+    std::cout << vase.length() << std::endl;
+  }
+
+  void parse_address(std::string_view cmd, uint64_t &i, Command::Address &addr);
+  void resolve_address(Command::Address addr, uint64_t *out_line);
+  Command parse(std::string cmd, bool eof);
+  void append(std::string text, uint64_t line);
+  void remove(uint64_t start_line, uint64_t end_line);
+  bool handle(std::string cmd, bool eof);
+};
+
 std::string summary();
 void help();
 void run(std::vector<std::string>);
diff --git a/include/internal/vase/iterators/line.h b/include/internal/vase/iterators/line.h
index 4e703a4..72514ee 100644
--- a/include/internal/vase/iterators/line.h
+++ b/include/internal/vase/iterators/line.h
@@ -24,8 +24,8 @@ struct Iterator {
   Shard *root;
   std::string line;
 
-  Iterator(Shard *root, uint64_t line_num)
-      : root(root), it(root, line_num, Direction::Forward) {
+  Iterator(Shard *root, uint64_t line_num, Direction dir)
+      : root(root), it(root, line_num, dir) {
     Shard::retain(root);
   }
 
@@ -63,9 +63,8 @@ struct Iterator {
     return *this;
   }
 
-  std::string &next() {
-    it.next(&line);
-    return line;
+  bool next() {
+    return it.next(&line);
   }
 
 private:
diff --git a/include/internal/vase/shard.h b/include/internal/vase/shard.h
index b1ea550..d0a5991 100644
--- a/include/internal/vase/shard.h
+++ b/include/internal/vase/shard.h
@@ -25,7 +25,7 @@ struct Shard {
   static void retain(Shard *n);
   static void release(Shard *n);
 
-  static Shard *from_file(std::filesystem::path path, OriginalBuffer *b);
+  static Shard *from_file(std::filesystem::path path, OriginalBuffer *b, bool posix_ending);
   static std::vector<Shard *> from_swap(std::filesystem::path path, OriginalBuffer *b);
 
   static std::pair<Shard *, Shard *> split(Shard *n, uint64_t offset);
@@ -34,6 +34,7 @@ struct Shard {
   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 {
@@ -62,54 +63,4 @@ struct Petal : Shard {
         source(source), pos(pos) {};
 };
 
-extern inline void dump_shard(Shard *node, int depth = 0) {
-  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 = static_cast<Branch *>(node);
-
-    std::cout << indent << "  left:\n";
-    dump_shard(branch->left, depth + 2);
-
-    std::cout << indent << "  right:\n";
-    dump_shard(branch->right, depth + 2);
-  } else {
-    auto *petal = static_cast<Petal *>(node);
-
-    std::cout
-      << indent << "  source=" << petal->source
-      << " pos=" << petal->pos
-      << " length=" << petal->length
-      << " lines=" << petal->lines
-      << "\n";
-  }
-
-  if (!depth)
-    std::cout << "\n\n";
-}
 } // namespace crib::internal::vase
diff --git a/include/internal/vase/vase.h b/include/internal/vase/vase.h
index 6a6f116..bbaf0d7 100644
--- a/include/internal/vase/vase.h
+++ b/include/internal/vase/vase.h
@@ -43,6 +43,15 @@ struct Vase {
   OriginalBuffer *original;
   AppendBuffer *append;
   Shard *root;
+
+#ifdef _WIN32
+  bool posix_ending = false;
+  bool using_crlf = true;
+#else
+  bool posix_ending = true;
+  bool using_crlf = false;
+#endif
+
   std::filesystem::path path;
   std::filesystem::path swapdir;
 
@@ -50,15 +59,18 @@ struct Vase {
   ~Vase();
 
   uint64_t length();
+  uint64_t lines();
   std::string to_string();
   std::string to_string(Range range);
 
-  Iterator iterate(uint64_t line);
+  Iterator iterate(uint64_t line, Direction dir);
 
   void insert(Point *point, char key);
+  void insert(Point *point, std::string_view str);
   void insert(Point *point, const char *data, uint64_t len);
   void erase(Point *point, uint64_t amount, Direction dir);
   void erase(Range range);
+  void replace(Range range, std::string_view str);
   void replace(Range range, const char *data, uint64_t len);
 
   void move_clusters(Point *point, uint64_t amount, Direction dir);
diff --git a/src/commands/ed/ed.cc b/src/commands/ed/ed.cc
index 2376dba..d9919b0 100644
--- a/src/commands/ed/ed.cc
+++ b/src/commands/ed/ed.cc
@@ -1,11 +1,40 @@
 #include "commands/ed/ed.h"
+#include "cli.h"
 
 namespace crib::commands::ed {
 std::string summary() {
   return "A POSIX-compliant line editor.";
 }
+
 void help() {}
+
 void run(std::vector<std::string> args) {
-  return;
+  std::string prompt = "";
+  std::filesystem::path filepath;
+  bool suppress = false;
+  for (size_t i = 1; i < args.size(); i++) {
+    if (args[i] == "-p") {
+      i++;
+      if (i >= args.size())
+        throw crib::cli::cli_error("Prompt not specified!", 1);
+      prompt = args[i];
+    } else if (args[i] == "-s") {
+      suppress = true;
+    } else {
+      if (filepath.string().size())
+        throw crib::cli::cli_error("Invalid arguments given.", 1);
+      filepath = args[i];
+    }
+  }
+  Ed ed(filepath, suppress, prompt);
+  std::string command;
+  while (true) {
+    std::string cmd;
+    if (ed.prompt_mode)
+      std::cout << ed.prompt;
+    bool eof = !std::getline(std::cin, cmd);
+    if (!ed.handle(cmd, eof))
+      return;
+  }
 }
 } // namespace crib::commands::ed
diff --git a/src/commands/ed/edit.cc b/src/commands/ed/edit.cc
new file mode 100644
index 0000000..17ebde6
--- /dev/null
+++ b/src/commands/ed/edit.cc
@@ -0,0 +1,21 @@
+#include "commands/ed/ed.h"
+
+namespace crib::commands::ed {
+void Ed::append(std::string text, uint64_t line) {
+  using namespace crib::internal::vase;
+  Point p = {line, 0};
+  if (!vase.lines()) {
+    text.pop_back();
+  } else if (line == vase.lines()) {
+    p.row--;
+    p.col = UINT64_MAX;
+    text = "\n" + text;
+    text.pop_back();
+  }
+  vase.insert(&p, text);
+}
+
+void Ed::remove(uint64_t start_line, uint64_t end_line) {
+  vase.erase({{start_line - 1, 0}, {end_line, 0}});
+}
+} // namespace crib::commands::ed
diff --git a/src/commands/ed/handle.cc b/src/commands/ed/handle.cc
new file mode 100644
index 0000000..5e9c1a1
--- /dev/null
+++ b/src/commands/ed/handle.cc
@@ -0,0 +1,254 @@
+#include "commands/ed/ed.h"
+
+namespace crib::commands::ed {
+bool Ed::handle(std::string cmd, bool eof) {
+  using namespace crib::internal::vase;
+  try {
+    if (line > vase.lines())
+      line = vase.lines();
+    Command command = parse(cmd, eof);
+    bool was_quitting = quitting;
+    quitting = false;
+    switch (command.type) {
+    case Command::Type::Quit:
+      if (modified && !was_quitting) {
+        quitting = true;
+        throw ed_error("Buffer modified.");
+      } else {
+        return false;
+      }
+    case Command::Type::ForceQuit:
+      return false;
+    case Command::Type::None: {
+      if (command.start.type != Command::Address::Type::None) {
+        if (command.address_flags & Command::RANGE)
+          resolve_address(command.end, &line);
+        else
+          resolve_address(command.start, &line);
+      } else {
+        line++;
+      }
+      if (line == 0)
+        throw ed_error("Line 0 is invalid.");
+      if (line > vase.lines())
+        throw ed_error("Line position too high.");
+      Iterator it = vase.iterate(line - 1, Direction::Backward);
+      it.next();
+      std::cout << it.line << std::endl;
+    } break;
+    case Command::Type::Invalid:
+      throw ed_error("Invalid command.");
+    case Command::Type::HelpToggle:
+      help_mode = !help_mode;
+      if (help_mode && last_message != "")
+        std::cout << last_message << std::endl;
+      break;
+    case Command::Type::Help:
+      if (last_message != "")
+        std::cout << last_message << std::endl;
+      break;
+    case Command::Type::PromptToggle:
+      prompt_mode = !prompt_mode;
+      break;
+    case Command::Type::Print: {
+      uint64_t line_start = line;
+      uint64_t line_end = line;
+      if (command.start.type != Command::Address::Type::None) {
+        resolve_address(command.start, &line_start);
+        line_end = line_start;
+        if (command.address_flags & Command::RANGE)
+          resolve_address(command.end, &line_end);
+      }
+      if (line_start == 0)
+        throw ed_error("Line 0 is invalid.");
+      if (line_end < line_start)
+        throw ed_error("Invalid address range.");
+      Iterator it = vase.iterate(line_start - 1, Direction::Forward);
+      while (it.next() && line_start++ <= line_end)
+        std::cout << it.line << std::endl;
+      line = line_end;
+    } break;
+    case Command::Type::Number: {
+      uint64_t line_start = line;
+      uint64_t line_end = line;
+      if (command.start.type != Command::Address::Type::None) {
+        resolve_address(command.start, &line_start);
+        line_end = line_start;
+        if (command.address_flags & Command::RANGE)
+          resolve_address(command.end, &line_end);
+      }
+      if (line_start == 0)
+        throw ed_error("Line 0 is invalid.");
+      if (line_end < line_start)
+        throw ed_error("Invalid address range.");
+      Iterator it = vase.iterate(line_start - 1, Direction::Forward);
+      while (it.next() && line_start <= line_end)
+        std::cout << line_start++ << "\t" << it.line << std::endl;
+      line = line_end;
+    } break;
+    case Command::Type::Append: {
+      std::string text;
+      std::string cline;
+      uint64_t line_count = 0;
+      while (std::getline(std::cin, cline)) {
+        if (cline == ".")
+          break;
+        line_count++;
+        text.append(cline);
+        text.push_back('\n');
+      }
+      if (std::cin.eof())
+        throw ed_error("EOF reached before '.' during text input.");
+      if (command.start.type != Command::Address::Type::None) {
+        if (command.address_flags & Command::RANGE)
+          resolve_address(command.end, &line);
+        else
+          resolve_address(command.start, &line);
+      }
+      if (text.empty()) {
+        if (line == 0)
+          line = 1;
+        break;
+      }
+      vase.snapshot();
+      append(text, line);
+      modified = true;
+      line += line_count;
+    } break;
+    case Command::Type::Change: {
+      uint64_t line_start = line;
+      uint64_t line_end = line;
+      if (command.start.type != Command::Address::Type::None) {
+        resolve_address(command.start, &line_start);
+        if (line_start == 0)
+          line_start = 1;
+        line_end = line_start;
+        if (command.address_flags & Command::RANGE)
+          resolve_address(command.end, &line_end);
+      }
+      if (line_end < line_start)
+        throw ed_error("Invalid address range.");
+      std::string text;
+      std::string cline;
+      uint64_t line_count = 0;
+      while (std::getline(std::cin, cline)) {
+        if (cline == ".")
+          break;
+        line_count++;
+        text.append(cline);
+        text.push_back('\n');
+      }
+      if (std::cin.eof())
+        throw ed_error("EOF reached before '.' during text input.");
+      vase.snapshot();
+      remove(line_start, line_end);
+      line = line_start;
+      if (text.empty())
+        break;
+      append(text, line);
+      modified = true;
+      line += line_count;
+    } break;
+    case Command::Type::Delete: {
+      uint64_t line_start = line;
+      uint64_t line_end = line;
+      if (command.start.type != Command::Address::Type::None) {
+        resolve_address(command.start, &line_start);
+        if (line_start == 0)
+          line_start = 1;
+        line_end = line_start;
+        if (command.address_flags & Command::RANGE)
+          resolve_address(command.end, &line_end);
+      }
+      if (line_end < line_start)
+        throw ed_error("Invalid address range.");
+      vase.snapshot();
+      vase.erase({{line_start - 1, 0}, {line_end, 0}});
+      modified = true;
+      line = line_start;
+      if (line > vase.lines())
+        line = vase.lines();
+    } break;
+    case Command::Type::Write: {
+      std::string path = command.argument;
+      if (path.empty()) {
+        path = vase.path;
+        if (path.empty())
+          throw ed_error("Need filename to write to.");
+      }
+      uint64_t line_start = 1;
+      uint64_t line_end = vase.lines();
+      if (vase.lines() == 0)
+        line_start = line_end = 0;
+      if (command.start.type != Command::Address::Type::None) {
+        resolve_address(command.start, &line_start);
+        line_end = line_start;
+        if (command.address_flags & Command::RANGE)
+          resolve_address(command.end, &line_end);
+      }
+      if (vase.lines() && line_start == 0)
+        throw ed_error("Line 0 is invalid.");
+      if (line_end < line_start)
+        throw ed_error("Invalid address range.");
+      uint64_t bytes = 0;
+      if (path[0] == '!') {
+        FILE *pipe = popen(path.c_str() + 1, "w");
+        if (!pipe)
+          throw ed_error("Error starting command.");
+        Iterator it = vase.iterate(line_start - 1, Direction::Forward);
+        while (it.next() && line_start++ <= line_end) {
+          it.line += '\n';
+          bytes += it.line.size();
+          if (fputs(it.line.c_str(), pipe) == EOF) {
+            pclose(pipe);
+            throw ed_error("Error writing to command.");
+          }
+        }
+        if (pclose(pipe) == -1)
+          throw ed_error("Error closing command.");
+      } else {
+        vase.path = path;
+        std::ofstream file(path, std::ios::out | std::ios::trunc);
+        if (!file)
+          throw ed_error("Error writing to file.");
+        Iterator it = vase.iterate(line_start - 1, Direction::Forward);
+        while (it.next() && line_start++ <= line_end) {
+          file << it.line << '\n';
+          bytes += it.line.size() + 1;
+        }
+        if (!file)
+          throw ed_error("Error writing to file.");
+        modified = false;
+      }
+      if (!suppress_mode)
+        std::cout << bytes << std::endl;
+    } break;
+    case Command::Type::Dump:
+      Shard::dump(vase.root);
+      break;
+    }
+    if (command.suffix) {
+      Iterator it = vase.iterate(line - 1, Direction::Forward);
+      it.next();
+      switch (command.suffix) {
+      case 'p':
+        std::cout << it.line << std::endl;
+        break;
+      case 'n':
+        std::cout << line << "\t" << it.line << std::endl;
+        break;
+      case 'l':
+        // TODO: escaping.
+        std::cout << it.line << std::endl;
+        break;
+      }
+    }
+  } catch (ed_error &e) {
+    last_message = e.what();
+    std::cout << "?" << std::endl;
+    if (help_mode)
+      std::cout << e.what() << std::endl;
+  }
+  return true;
+}
+} // namespace crib::commands::ed
diff --git a/src/commands/ed/parsers/address.cc b/src/commands/ed/parsers/address.cc
new file mode 100644
index 0000000..ee68937
--- /dev/null
+++ b/src/commands/ed/parsers/address.cc
@@ -0,0 +1,178 @@
+#include "commands/ed/ed.h"
+
+namespace crib::commands::ed {
+void Ed::parse_address(std::string_view cmd, uint64_t &i, Command::Address &addr) {
+  auto skip_space = [&] {
+    while (i < cmd.size() && (cmd[i] == ' ' || cmd[i] == '\t'))
+      ++i;
+  };
+  skip_space();
+  if (i >= cmd.size()) {
+    addr.type = Command::Address::Type::None;
+    return;
+  }
+  switch (cmd[i]) {
+  case '.':
+    addr.type = Command::Address::Type::Current;
+    i++;
+    break;
+  case '$':
+    addr.type = Command::Address::Type::Last;
+    i++;
+    break;
+  case '\'':
+    addr.type = Command::Address::Type::Mark;
+    i++;
+    if (i < cmd.size() && 'a' <= cmd[i] && cmd[i] <= 'z')
+      i++;
+    else
+      throw ed_error("Invalid mark.");
+    addr.mark = cmd[i];
+    break;
+  case '/': {
+    addr.type = Command::Address::Type::SearchForward;
+    i++;
+    uint64_t start = i;
+    while (true) {
+      if (i >= cmd.size())
+        break;
+      if (cmd[i] == '/')
+        break;
+      else if (cmd[i] == '\\')
+        i += 2;
+      else if (cmd[i] == '[' && i + 1 < cmd.size() && cmd[i + 1] == '[')
+        while (i < cmd.size() && !(cmd[i - 1] == ']' && cmd[i] == ']'))
+          i++;
+      else if (cmd[i] == '[')
+        while (i < cmd.size() && cmd[i] != ']')
+          i++;
+      else
+        i++;
+    }
+    addr.regex = cmd.substr(start, i - start);
+  } break;
+  case '?': {
+    addr.type = Command::Address::Type::SearchBackward;
+    i++;
+    uint64_t start = i;
+    while (true) {
+      if (i >= cmd.size())
+        break;
+      if (cmd[i] == '?')
+        break;
+      else if (cmd[i] == '\\')
+        i += 2;
+      else if (cmd[i] == '[' && i + 1 < cmd.size() && cmd[i + 1] == '[')
+        while (i < cmd.size() && !(cmd[i - 1] == ']' && cmd[i] == ']'))
+          i++;
+      else if (cmd[i] == '[')
+        while (i < cmd.size() && cmd[i] != ']')
+          i++;
+      else
+        i++;
+    }
+    addr.regex = cmd.substr(start, i - start);
+  } break;
+  case '+': {
+    i++;
+    skip_space();
+    uint64_t start = i;
+    int64_t num = 0;
+    while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
+      num = num * 10 + (cmd[i] - '0');
+      i++;
+    }
+    if (start == i)
+      num = 1;
+    addr.offset += num;
+  } break;
+  case '-': {
+    i++;
+    skip_space();
+    uint64_t start = i;
+    int64_t num = 0;
+    while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
+      num = num * 10 + (cmd[i] - '0');
+      i++;
+    }
+    if (start == i)
+      num = 1;
+    addr.offset -= num;
+  } break;
+  default: {
+    if ('0' <= cmd[i] && cmd[i] <= '9') {
+      int64_t num = 0;
+      addr.type = Command::Address::Type::Number;
+      while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
+        num = num * 10 + (cmd[i] - '0');
+        i++;
+      }
+      addr.number = num;
+    } else {
+      addr.type = Command::Address::Type::None;
+      return;
+    }
+    break;
+  }
+  }
+  skip_space();
+  while (i < cmd.size() && (cmd[i] == '+' || cmd[i] == '-' || ('0' <= cmd[i] && cmd[i] <= '9'))) {
+    bool positive = cmd[i] != '-';
+    if (cmd[i] == '+' || cmd[i] == '-') {
+      i++;
+      skip_space();
+    }
+    uint64_t start = i;
+    int64_t num = 0;
+    while (i < cmd.size() && '0' <= cmd[i] && cmd[i] <= '9') {
+      num = num * 10 + (cmd[i] - '0');
+      i++;
+    }
+    if (start == i)
+      num = 1;
+    addr.offset += positive ? num : -num;
+    skip_space();
+  }
+}
+
+void Ed::resolve_address(Command::Address addr, uint64_t *out_line) {
+  switch (addr.type) {
+  case Command::Address::Type::None:
+    break;
+  case Command::Address::Type::Current:
+    *out_line = line;
+    if (*out_line > vase.lines())
+      *out_line = vase.lines();
+    break;
+  case Command::Address::Type::Number:
+    *out_line = addr.number;
+    break;
+  case Command::Address::Type::Last:
+    *out_line = vase.lines();
+    break;
+  case Command::Address::Type::Mark:
+    *out_line = marks[addr.mark - 'a'];
+    if (!*out_line)
+      throw ed_error("Unset mark used.");
+    break;
+  case Command::Address::Type::SearchForward:
+    if (addr.regex == "")
+      addr.regex = last_regex;
+    last_regex = addr.regex;
+    // TODO: use vase.regex_search(regex, range, options);
+    break;
+  case Command::Address::Type::SearchBackward:
+    if (addr.regex == "")
+      addr.regex = last_regex;
+    last_regex = addr.regex;
+    // TODO
+    break;
+  }
+  if ((int64_t)*out_line + addr.offset < 0)
+    throw ed_error("Line position can't be negative.");
+  else
+    *out_line += addr.offset;
+  if (*out_line > vase.lines())
+    throw ed_error("Line position too high.");
+}
+} // namespace crib::commands::ed
diff --git a/src/commands/ed/parsers/command.cc b/src/commands/ed/parsers/command.cc
new file mode 100644
index 0000000..4063ba4
--- /dev/null
+++ b/src/commands/ed/parsers/command.cc
@@ -0,0 +1,115 @@
+#include "commands/ed/ed.h"
+
+namespace crib::commands::ed {
+Command Ed::parse(std::string cmd, bool eof) {
+  Command command = {};
+  if (eof)
+    return (command.type = Command::Type::Quit, command);
+  uint64_t i = 0;
+  auto skip_space = [&] {
+    while (i < cmd.size() && (cmd[i] == ' ' || cmd[i] == '\t'))
+      ++i;
+  };
+  Command::Address first;
+  Command::Address second;
+  parse_address(cmd, i, first);
+  bool have_range = false;
+  while (i < cmd.size() && (cmd[i] == ',' || cmd[i] == ';')) {
+    char sep = cmd[i++];
+    if (sep == ';')
+      resolve_address(first, &line);
+    command.address_flags = sep == ';' ? Command::SEMICOLON : 0;
+    if (have_range)
+      first = second;
+    parse_address(cmd, i, second);
+    have_range = true;
+  }
+  if (have_range) {
+    if (first.type != Command::Address::Type::None
+        && second.type == Command::Address::Type::None) {
+      second = first;
+    } else if (first.type == Command::Address::Type::None) {
+      if (command.address_flags & Command::SEMICOLON) {
+        first.type = Command::Address::Type::Current;
+      } else {
+        first.type = Command::Address::Type::Number;
+        first.number = 1;
+      }
+      if (second.type == Command::Address::Type::None)
+        second.type = Command::Address::Type::Last;
+    }
+    command.address_flags |= Command::RANGE;
+    command.start = first;
+    command.end = second;
+  } else {
+    command.start = first;
+  }
+  if (i >= cmd.size()) {
+    command.type = Command::Type::None;
+    return command;
+  }
+  switch (cmd[i]) {
+  case 'q':
+    command.type = Command::Type::Quit;
+    return command;
+  case 'Q':
+    command.type = Command::Type::ForceQuit;
+    return command;
+  case 'p':
+    command.type = Command::Type::Print;
+    i++;
+    break;
+  case 'n':
+    command.type = Command::Type::Number;
+    i++;
+    break;
+  case 'P':
+    command.type = Command::Type::PromptToggle;
+    i++;
+    break;
+  case 'H':
+    command.type = Command::Type::HelpToggle;
+    i++;
+    break;
+  case 'h':
+    command.type = Command::Type::Help;
+    i++;
+    break;
+  case 'a':
+    command.type = Command::Type::Append;
+    i++;
+    break;
+  case 'c':
+    command.type = Command::Type::Change;
+    i++;
+    break;
+  case 'd':
+    command.type = Command::Type::Delete;
+    i++;
+    break;
+  case 'w':
+    command.type = Command::Type::Write;
+    i++;
+    if (i >= cmd.size())
+      return command;
+    if (cmd[i] == ' ' || cmd[i] == '\t')
+      skip_space();
+    else
+      throw ed_error("Invalid command.");
+    command.argument = cmd.substr(i);
+    return command;
+  case '#':
+    command.type = Command::Type::Dump;
+    i++;
+    break;
+  }
+  if (i < cmd.size()) {
+    if (cmd[i] == 'l' || cmd[i] == 'n' || cmd[i] == 'p')
+      command.suffix = cmd[i++];
+    skip_space();
+    if (i != cmd.size())
+      throw ed_error("Invalid command.");
+  }
+  return command;
+}
+} // namespace crib::commands::ed
diff --git a/src/commands/ed/parsers/regex.cc b/src/commands/ed/parsers/regex.cc
new file mode 100644
index 0000000..e69de29
diff --git a/src/internal/vase/iterators/petal.cc b/src/internal/vase/iterators/petal.cc
index 2eb3eff..0049e44 100644
--- a/src/internal/vase/iterators/petal.cc
+++ b/src/internal/vase/iterators/petal.cc
@@ -88,16 +88,24 @@ void PetalIterator::seek_line(uint64_t line) {
     } else {
       auto *b = (Branch *)curr;
       uint64_t left_lines = b->left->lines;
-      if (line <= left_lines) {
-        if (dir == Direction::Forward)
+      if (dir == Direction::Forward) {
+        if (line < left_lines) {
           stack.push_back(b->right);
-        curr = b->left;
+          curr = b->left;
+        } else {
+          line -= left_lines;
+          global_offset += b->left->length;
+          curr = b->right;
+        }
       } else {
-        line -= left_lines;
-        if (dir == Direction::Backward)
+        if (line <= left_lines) {
+          curr = b->left;
+        } else {
+          line -= left_lines;
           stack.push_back(b->left);
-        global_offset += b->left->length;
-        curr = b->right;
+          global_offset += b->left->length;
+          curr = b->right;
+        }
       }
     }
   }
diff --git a/src/internal/vase/shard.cc b/src/internal/vase/shard.cc
index 4bebc8f..65abb2c 100644
--- a/src/internal/vase/shard.cc
+++ b/src/internal/vase/shard.cc
@@ -91,7 +91,7 @@ Shard *balance(Shard *node) {
 
 Shard *Shard::merge(Shard *a, Shard *b) {
   if (!a)
-    return b ? (Shard::retain(b), b) : nullptr;
+    return (Shard::retain(b), b);
   if (!b)
     return (Shard::retain(a), a);
 
@@ -205,7 +205,7 @@ Shard *Shard::build(Shard **pieces, uint64_t lo, uint64_t hi) {
   return node;
 }
 
-Shard *Shard::from_file(std::filesystem::path path, OriginalBuffer *o) {
+Shard *Shard::from_file(std::filesystem::path path, OriginalBuffer *o, bool posix_ending) {
   int dest_fd = o->fd;
   if (dest_fd == -1)
     return nullptr;
@@ -214,6 +214,19 @@ Shard *Shard::from_file(std::filesystem::path path, OriginalBuffer *o) {
     return nullptr;
 
   uint64_t total = std::filesystem::file_size(path);
+  if (posix_ending && total > 0) {
+    char last;
+    char s_last;
+    if (pread(src_fd, &last, 1, (off_t)(total - 1)) != 1)
+      return nullptr;
+    if (pread(src_fd, &s_last, 1, (off_t)(total - 2)) != 1)
+      return nullptr;
+    if (last == '\n') {
+      total--;
+      if (s_last == '\r')
+        total--;
+    }
+  }
   std::vector<Shard *> pieces;
   uint64_t pos = 0;
   pieces.reserve((total + PETAL_SIZE_MAX - 1) / PETAL_SIZE_MAX);
@@ -257,4 +270,54 @@ Shard *Shard::from_file(std::filesystem::path path, OriginalBuffer *o) {
     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 crib::internal::vase
diff --git a/src/internal/vase/vase.cc b/src/internal/vase/vase.cc
index 1eafa63..86d923a 100644
--- a/src/internal/vase/vase.cc
+++ b/src/internal/vase/vase.cc
@@ -8,12 +8,12 @@ Vase::Vase(std::filesystem::path path, std::filesystem::path swapdir)
   append = new AppendBuffer(swapdir);
   original = new OriginalBuffer(swapdir);
   if (std::filesystem::is_regular_file(path))
-    root = Shard::from_file(path, original);
+    root = Shard::from_file(path, original, posix_ending);
   else
     root = nullptr;
+  history_top = 0;
   history.push_back(root);
   Shard::retain(root);
-  history_top = 0;
 }
 
 Vase::~Vase() {
@@ -25,22 +25,38 @@ Vase::~Vase() {
 }
 
 uint64_t Vase::length() {
+  if (!root)
+    return 0;
   return root->length;
 }
 
+uint64_t Vase::lines() {
+  if (!root)
+    return 0;
+  return root->lines + 1;
+}
+
 std::string Vase::to_string() {
   std::string out;
+  if (!root)
+    return out;
   PetalIterator it(root, Direction::Forward);
   it.seek_offset(0);
   const char *data;
   uint64_t len;
   while (it.next(&data, &len))
     out.append(data, len);
+  if (posix_ending)
+    out.append("\n");
   return out;
 }
 
 std::string Vase::to_string(Range range) {
+  clamp(&range.start);
+  clamp(&range.end);
   std::string out;
+  if (!root)
+    return out;
   PetalIterator it(root, Direction::Forward);
   uint64_t start = offset_of(range.start);
   it.seek_offset(start);
@@ -55,8 +71,8 @@ std::string Vase::to_string(Range range) {
   return out;
 }
 
-Iterator Vase::iterate(uint64_t line) {
-  return Iterator(root, line);
+Iterator Vase::iterate(uint64_t line, Direction dir) {
+  return Iterator(root, line, dir);
 }
 
 bool Vase::undo() {
@@ -100,6 +116,8 @@ void Vase::prune_history(uint64_t n) {
 }
 
 bool Vase::save() {
+  if (!root)
+    return true;
   std::ofstream file(path, std::ios::binary);
   if (!file)
     return false;
@@ -112,6 +130,10 @@ bool Vase::save() {
     if (!file)
       return false;
   }
+  if (posix_ending)
+    file.write("\n", 1);
+  if (!file)
+    return false;
   return true;
 }
 
@@ -137,6 +159,10 @@ void Vase::insert(Point *point, char key) {
     point->col++;
 }
 
+void Vase::insert(Point *point, std::string_view str) {
+  insert(point, str.data(), str.size());
+}
+
 void Vase::insert(Point *point, const char *data, uint64_t len) {
   while (len) {
     uint64_t chunk_size = std::min<uint64_t>(len, PETAL_SIZE_MAX);
@@ -229,12 +255,17 @@ void Vase::erase(Range range) {
   root = new_root;
 }
 
+void Vase::replace(Range range, std::string_view str) {
+  replace(range, str.data(), str.size());
+}
+
 void Vase::replace(Range range, const char *data, uint64_t len) {
   erase(range);
   insert(&range.start, data, len);
 }
 
 uint64_t Vase::offset_of(Point point) {
+  clamp(&point);
   LineIterator it(root, point.row, Direction::Forward);
   std::string line;
   uint64_t offset = 0;
@@ -296,6 +327,7 @@ Point Vase::point_of(uint64_t offset) {
     ptr += next_len;
     p.col++;
   }
+  clamp(&p);
   return p;
 }
 
@@ -363,11 +395,19 @@ void Vase::move_clusters(Point *point, uint64_t amount, Direction dir) {
       }
     }
   }
+  clamp(point);
 }
 
 void Vase::clamp(Point *point) {
-  if (point->row > root->lines)
+  if (!root) {
+    point->row = 0;
+    point->col = 0;
+    return;
+  }
+  if (point->row > root->lines) {
     point->row = root->lines;
+    point->col = UINT64_MAX;
+  }
   LineIterator it(root, point->row, Direction::Forward);
   std::string line;
   uint64_t clusters = 0;