diff --git a/src/future/exec/ExecFuture.php b/src/future/exec/ExecFuture.php
--- a/src/future/exec/ExecFuture.php
+++ b/src/future/exec/ExecFuture.php
@@ -56,6 +56,8 @@
     2 => array('pipe', 'w'),  // stderr
   );
 
+  private $descriptors;
+
 
 /* -(  Creating ExecFutures  )----------------------------------------------- */
 
@@ -195,6 +197,19 @@
     return $this;
   }
 
+  /**
+   * Set the file descriptors which will be passed down to the underlying
+   * process; defaults to all of the standard handles being pipes back to this
+   * class.  Overrides configuration set by @{method:setUseWindowsFileStreams}.
+   *
+   * @param array As passed to `proc_open`.
+   * @return this
+   * @task config
+   */
+  public function setDescriptors($descs) {
+    $this->descriptors = $descs;
+    return $this;
+  }
 
 /* -(  Interacting With Commands  )------------------------------------------ */
 
@@ -626,8 +641,9 @@
         $trap = null;
       }
 
-      $spec = self::$descriptorSpec;
-      if ($this->useWindowsFileStreams) {
+      if ($this->descriptors) {
+        $spec = $this->descriptors;
+      } else if ($this->useWindowsFileStreams) {
         $this->windowsStdoutTempFile = new TempFile();
         $this->windowsStderrTempFile = new TempFile();
 
@@ -642,6 +658,8 @@
             'Unable to create temporary files for '.
             'Windows stdout / stderr streams'));
         }
+      } else {
+        $spec = self::$descriptorSpec;
       }
 
       $proc = @proc_open(
@@ -651,7 +669,7 @@
         $cwd,
         $env);
 
-      if ($this->useWindowsFileStreams) {
+      if (!$this->descriptors && $this->useWindowsFileStreams) {
         fclose($spec[1]);
         fclose($spec[2]);
         $pipes = array(
@@ -682,6 +700,10 @@
             $err));
       }
 
+      // If different descriptors were passed, we may have an array without
+      // values for all of its indices.  Merge null values in.
+      $pipes = $pipes + array(null, null, null);
+
       $this->pipes = $pipes;
       $this->proc  = $proc;
 
@@ -693,9 +715,9 @@
         // through temporary files, and then use stream_select to determine
         // if there's more data to read.
 
-        if ((!stream_set_blocking($stdout, false)) ||
-            (!stream_set_blocking($stderr, false)) ||
-            (!stream_set_blocking($stdin,  false))) {
+        if (($stdout && !stream_set_blocking($stdout, false)) ||
+            ($stderr && !stream_set_blocking($stderr, false)) ||
+            ($stdin  && !stream_set_blocking($stdin,  false))) {
           $this->__destruct();
           throw new Exception(pht('Failed to set streams nonblocking.'));
         }
@@ -741,7 +763,7 @@
       $max_stderr_read_bytes = $read_buffer_size - strlen($this->stderr);
     }
 
-    if ($max_stdout_read_bytes > 0) {
+    if ($max_stdout_read_bytes > 0 && $stdout) {
       $this->stdout .= $this->readAndDiscard(
         $stdout,
         $this->getStdoutSizeLimit() - strlen($this->stdout),
@@ -749,7 +771,7 @@
         $max_stdout_read_bytes);
     }
 
-    if ($max_stderr_read_bytes > 0) {
+    if ($max_stderr_read_bytes > 0 && $stderr) {
       $this->stderr .= $this->readAndDiscard(
         $stderr,
         $this->getStderrSizeLimit() - strlen($this->stderr),
@@ -769,7 +791,7 @@
     }
 
     if ($is_done) {
-      if ($this->useWindowsFileStreams) {
+      if (!$this->descriptors && $this->useWindowsFileStreams) {
         fclose($stdout);
         fclose($stderr);
       }
diff --git a/src/future/exec/__tests__/ExecFutureTestCase.php b/src/future/exec/__tests__/ExecFutureTestCase.php
--- a/src/future/exec/__tests__/ExecFutureTestCase.php
+++ b/src/future/exec/__tests__/ExecFutureTestCase.php
@@ -152,4 +152,34 @@
     $future->resolve();
   }
 
+  public function testHigherFileDescriptors() {
+    $temp = new TempFile();
+    $future = new ExecFuture('echo yay >&3');
+    $future->setDescriptors(
+      array(
+        0 => array('pipe', 'r'),  // stdin
+        1 => array('pipe', 'w'),  // stdout
+        2 => array('pipe', 'w'),  // stderr
+        3 => array('file', $temp, 'w'),
+      ));
+
+    list($stdout) = $future->resolvex();
+    $this->assertEqual('', $stdout);
+    $this->assertEqual("yay\n", Filesystem::readFile($temp));
+  }
+
+  public function testFeedStdin() {
+    $temp = new TempFile();
+    Filesystem::writeFile($temp, 'yay');
+    $future = new ExecFuture('cat');
+    $future->setDescriptors(
+      array(
+        0 => array('file', $temp, 'r'), // stdin
+        1 => array('pipe', 'w'),  // stdout
+        2 => array('pipe', 'w'),  // stderr
+      ));
+
+    list($stdout) = $future->resolvex();
+    $this->assertEqual('yay', $stdout);
+  }
 }