Add a new script forked_adb_logcat_monitor.py.

build/android/forked_adb_logcat_monitor.py

+#!/usr/bin/env python
+#
+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Saves logcats from all connected devices but in a separate, forked process.
+
+Usage: forked_adb_logcat_monitor.py <base_dir> [<adb_binary_path>]
+
+This script is similar to adb_logcat_monitor.py, but spawns logcat watchers in
+separate forked process. See adb_logcat_monitor.py for more info.
+"""
+
+import os
+import sys
+
+import adb_logcat_monitor
+
+if __name__ == '__main__':

[navabi, 2013/10/03 23:51:04]

move the body of this into a main function.
if 2 <= len(sys.argv) <= 3:
  sys.exit(main(*sys.argv[...]))

+  if 2 <= len(sys.argv) <= 3:
+    print 'adb_logcat_monitor: Initializing'
+    # Spawn a detached child process.
+    try:
+      pid = os.fork()
+      if pid > 0:
+        # exit first parent
+        sys.exit(0)
+    except OSError, e:
+      sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
+      sys.exit(1)
+
+    # decouple from parent environment
+    os.chdir("/")
+    os.setsid()
+    os.umask(0)
+
+    # do second fork

[navabi, 2013/10/03 23:51:04]

Why is there a second fork? For the adb_reboot_on_disconnect we only did one
fork. I tried to find the explanation for the second fork from the link, but it
refers to another link that doesn't work:
http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16

It would be good to have a comment explaining the need for the second fork.

+    try:
+      pid = os.fork()
+      if pid > 0:
+        # exit from second parent
+        sys.exit(0)
+    except OSError, e:
+      sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
+      sys.exit(1)
+
+    # redirect standard file descriptors
+    sys.stdout.flush()
+    sys.stderr.flush()
+    si = file('/dev/null', 'r')
+    so = file('/dev/null', 'a+')
+    se = file('/dev/null', 'a+', 0)
+    os.dup2(si.fileno(), sys.stdin.fileno())
+    os.dup2(so.fileno(), sys.stdout.fileno())
+    os.dup2(se.fileno(), sys.stderr.fileno())
+
+    sys.exit(adb_logcat_monitor.SpawnLogcatWatchers(*sys.argv[1:3]))
+
+  print 'Usage: %s <base_dir> [<adb_binary_path>]' % sys.argv[0]