Adds gru.daemonize() and example application. Simplifies running GNU Radio applications as background daemon processes instead of foreground applications.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@8191 221aa14e-8319-0410-a670-987f0aec2ac5

2 files changed, 104 insertions, 1 deletions

diff --git a/gnuradio-core/src/python/gnuradio/gruimpl/Makefile.am b/gnuradio-core/src/python/gnuradio/gruimpl/Makefile.am
index 7fbc6ec56..b2ed7e64b 100644
--- a/gnuradio-core/src/python/gnuradio/gruimpl/Makefile.am
+++ b/gnuradio-core/src/python/gnuradio/gruimpl/Makefile.am
@@ -35,6 +35,7 @@ grupython_PYTHON = 			\
 	os_read_exactly.py		\
 	sdr_1000.py			\
 	seq_with_cursor.py		\
-	socket_stuff.py			
+	socket_stuff.py			\
+	daemon.py
 
 CLEANFILES = *.pyc
diff --git a/gnuradio-core/src/python/gnuradio/gruimpl/daemon.py b/gnuradio-core/src/python/gnuradio/gruimpl/daemon.py
new file mode 100644
index 000000000..4fa972ad2
--- /dev/null
+++ b/gnuradio-core/src/python/gnuradio/gruimpl/daemon.py
@@ -0,0 +1,102 @@
+#
+# Copyright 2008 Free Software Foundation, Inc.
+# 
+# This file is part of GNU Radio
+# 
+# GNU Radio is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+# 
+# GNU Radio is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with GNU Radio; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+# 
+import os, sys, signal
+
+# Turn application into a background daemon process.
+#
+# When this function returns:
+#
+# 1) The calling process is disconnected from its controlling terminal
+#    and will not exit when the controlling session exits
+# 2) If a pidfile name is provided, it is created and the new pid is
+#    written into it.
+# 3) If a logfile name is provided, it is opened and stdout/stderr are
+#    redirected to it.
+# 4) The process current working directory is changed to '/' to avoid
+#    pinning any filesystem mounts.
+# 5) The process umask is set to 0111.
+#
+# The return value is the new pid.
+#
+# To create GNU Radio applications that operate as daemons, add a call to this
+# function after all initialization but just before calling gr.top_block.run()
+# or .start().
+#
+# Daemonized GNU Radio applications may be stopped by sending them a
+# SIGINT, SIGKILL, or SIGTERM, e.g., using 'kill pid' from the command line.
+#
+# If your application uses gr.top_block.run(), the flowgraph will be stopped
+# and the function will return.  You should allow your daemon program to exit
+# at this point.
+#
+# If your application uses gr.top_block.start(), you are responsible for hooking
+# the Python signal handler (see 'signal' module) and calling gr.top_block.stop()
+# on your top block, and otherwise causing your daemon process to exit.
+#
+
+def daemonize(pidfile=None, logfile=None):
+    # fork() into background
+    try:
+	pid = os.fork()
+    except OSError, e:
+	raise Exception, "%s [%d]" % (e.strerror, e.errno)
+
+    if pid == 0:	# First child of first fork()
+	# Become session leader of new session
+	os.setsid()
+	
+	# fork() into background again
+	try:
+	    pid = os.fork()
+	except OSError, e:
+	    raise Exception, "%s [%d]" % (e.strerror, e.errno)
+
+	if pid != 0:
+	    os._exit(0) # Second child of second fork()
+
+    else:		# Second child of first fork()
+	os._exit(0)
+	
+    os.umask(0111)
+
+    # Write pid
+    pid = os.getpid()
+    if pidfile is not None:
+	open(pidfile, 'w').write('%d\n'%pid)
+	
+    # Redirect streams
+    if logfile is not None:
+	lf = open(logfile, 'a+')
+	sys.stdout = lf
+	sys.stderr = lf
+
+    # Prevent pinning any filesystem mounts
+    os.chdir('/')
+
+    # Tell caller what pid to send future signals to
+    return pid
+
+if __name__ == "__main__":
+    import time
+    daemonize()
+    print "Hello, world, from daemon process."
+    time.sleep(20)
+    print "Goodbye, world, from daemon process."