child_process: expose UV_PROCESS_DETACHED as options.detached

doc/api/child_process.markdown

@@ -249,7 +249,7 @@ there is no IPC channel keeping it alive. When calling this method the
   * `customFds` {Array} **Deprecated** File descriptors for the child to use
     for stdio.  (See below)
   * `env` {Object} Environment key-value pairs
-  * `setsid` {Boolean}
+  * `detached` {Boolean} The child will be a process group leader.  (See below)
 * return: {ChildProcess object}
 
 Launches a new process with the given `command`, with  command line arguments in `args`.
@@ -342,7 +342,7 @@ index corresponds to a fd in the child.  The value is one of the following:
 
 1. `'pipe'` - Create a pipe between the child process and the parent process.
    The parent end of the pipe is exposed to the parent as a property on the
-   child_process object as `ChildProcess.stdio[fd]`. Pipes created for
+   `child_process` object as `ChildProcess.stdio[fd]`. Pipes created for
    fds 0 - 2 are also available as ChildProcess.stdin, ChildProcess.stdout
    and ChildProcess.stderr, respectively.
 2. `'ipc'` - Create an IPC channel for passing messages/file descriptors
@@ -387,6 +387,34 @@ Example:
     // startd-style interface.
     spawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });
 
+If the `detached` option is set, the child process will be made the leader of a
+new process group.  This makes it possible for the child to continue running 
+after the parent exits.
+
+By default, the parent will wait for the detached child to exit.  To prevent
+the parent from waiting for a given `child`, use the `child.unref()` method,
+and the parent's event loop will not include the child in its reference count.
+
+Example of detaching a long-running process and redirecting its output to a
+file:
+
+     var fs = require('fs'),
+         spawn = require('child_process').spawn,
+         out = fs.openSync('./out.log', 'a'),
+         err = fs.openSync('./out.log', 'a');
+
+     var child = spawn('prg', [], {
+       detached: 'true',
+       stdio: [ 'ignore', out, err ]
+     });
+
+     child.unref();
+
+When using the `detached` option to start a long-running process, the process
+will not stay running in the background unless it is provided with a `stdio`
+configuration that is not connected to the parent.  If the parent's `stdio` is
+inherited, the child will remain attached to the controlling terminal.
+
 There is a deprecated option called `customFds` which allows one to specify
 specific file descriptors for the stdio of the child process. This API was
 not portable to all platforms and therefore removed.
@@ -409,7 +437,6 @@ See also: `child_process.exec()` and `child_process.fork()`
   * `customFds` {Array} **Deprecated** File descriptors for the child to use
     for stdio.  (See above)
   * `env` {Object} Environment key-value pairs
-  * `setsid` {Boolean}
   * `encoding` {String} (Default: 'utf8')
   * `timeout` {Number} (Default: 0)
   * `maxBuffer` {Number} (Default: 200*1024)
@@ -467,7 +494,6 @@ the child process is killed.
   * `customFds` {Array} **Deprecated** File descriptors for the child to use
     for stdio.  (See above)
   * `env` {Object} Environment key-value pairs
-  * `setsid` {Boolean}
   * `encoding` {String} (Default: 'utf8')
   * `timeout` {Number} (Default: 0)
   * `maxBuffer` {Number} (Default: 200*1024)
@@ -490,7 +516,6 @@ leaner than `child_process.exec`. It has the same options.
 * `options` {Object}
   * `cwd` {String} Current working directory of the child process
   * `env` {Object} Environment key-value pairs
-  * `setsid` {Boolean}
   * `encoding` {String} (Default: 'utf8')
   * `timeout` {Number} (Default: 0)
 * Return: ChildProcess object

lib/child_process.js

@@ -602,12 +602,17 @@ var spawn = exports.spawn = function(file, args, options) {
     args: args,
     cwd: options ? options.cwd : null,
     windowsVerbatimArguments: !!(options && options.windowsVerbatimArguments),
+    detached: !!(options && options.detached),
     envPairs: envPairs,
     stdio: options ? options.stdio : null,
     uid: options ? options.uid : null,
     gid: options ? options.gid : null
   });
 
+  if (options && options.detached) {
+    child.unref();
+  }
+
   return child;
 };
 

src/process_wrap.cc

@@ -236,6 +236,11 @@ class ProcessWrap : public HandleWrap {
       options.flags |= UV_PROCESS_WINDOWS_VERBATIM_ARGUMENTS;
     }
 
+    //options.detached
+    if (js_options->Get(String::NewSymbol("detached"))->IsTrue()) {
+      options.flags |= UV_PROCESS_DETACHED;
+    }
+
     int r = uv_spawn(uv_default_loop(), &wrap->process_, options);
 
     if (r) {

test/fixtures/child-process-persistent.js

@@ -0,0 +1 @@
+setInterval(function () {}, 500);

test/simple/test-child-process-detached.js

@@ -0,0 +1,38 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var path = require('path');
+
+var spawn = require('child_process').spawn;
+var childPath = path.join(__dirname, '..', 'fixtures', 'child-process-persistent.js');
+
+var child = spawn(process.execPath, [ childPath ], {
+  detached: true,
+  stdio: 'ignore'
+});
+
+process.on('exit', function () {
+  process.kill(child.pid);
+  assert.throws(process.kill(child.pid), Error);
+});
+