diff --git a/src/filesystem/linesofalarge/LinesOfALarge.php b/src/filesystem/linesofalarge/LinesOfALarge.php
--- a/src/filesystem/linesofalarge/LinesOfALarge.php
+++ b/src/filesystem/linesofalarge/LinesOfALarge.php
@@ -42,7 +42,7 @@
   private $valid;
   private $eof;
 
-  private $delimiter      = "\n";
+  private $delimiter = "\n";
 
 
 /* -(  Configuration  )------------------------------------------------------ */
@@ -52,14 +52,18 @@
    * Change the "line" delimiter character, which defaults to "\n". This is
    * used to determine where each line ends.
    *
-   * @param string A one-byte delimiter character.
+   * If you pass `null`, data will be read from source as it becomes available,
+   * without looking for delimiters. You can use this to stream a large file or
+   * the output of a command which returns a large amount of data.
+   *
+   * @param string|null A one-byte delimiter character.
    * @return this
    * @task config
    */
   final public function setDelimiter($character) {
-    if (strlen($character) !== 1) {
+    if (($character !== null) && (strlen($character) !== 1)) {
       throw new Exception(
-        pht('Delimiter character MUST be one byte in length.'));
+        pht('Delimiter character must be one byte in length or null.'));
     }
     $this->delimiter = $character;
     return $this;
@@ -147,6 +151,16 @@
     // read.
     while (true) {
       if (strlen($this->buf)) {
+
+        // If we don't have a delimiter, return the entire buffer.
+        if ($this->delimiter === null) {
+          $this->num++;
+          $this->line = substr($this->buf, $this->pos);
+          $this->buf = '';
+          $this->pos = 0;
+          return;
+        }
+
         // If we already have some data buffered, try to get the next line from
         // the buffer. Search through the buffer for a delimiter. This should be
         // the common case.
diff --git a/src/utils/PhutilRope.php b/src/utils/PhutilRope.php
--- a/src/utils/PhutilRope.php
+++ b/src/utils/PhutilRope.php
@@ -68,6 +68,34 @@
 
 
   /**
+   * Get prefix bytes of the rope, up to some maximum size.
+   *
+   * @param int Maximum number of bytes to read.
+   * @return string Bytes.
+   */
+  public function getPrefixBytes($length) {
+    $result = array();
+
+    $remaining_bytes = $length;
+    foreach ($this->buffers as $buf) {
+      $length = strlen($buf);
+      if ($length <= $remaining_bytes) {
+        $result[] = $buf;
+        $remaining_bytes -= $length;
+      } else {
+        $result[] = substr($buf, 0, $remaining_bytes);
+        $remaining_bytes = 0;
+      }
+      if (!$remaining_bytes) {
+        break;
+      }
+    }
+
+    return implode('', $result);
+  }
+
+
+  /**
    * Return the entire rope as a normal string.
    *
    * @return string Normal string.