This module provides support for daemonizing a process. It provides flexibility as to where the standard file descriptors (stdin, stdout and stderr) are connected after daemonization has occurred.
daemonize makes the executing process a daemon.
See Chapter 13 of Advanced Programming in the UNIX Environment Second Edition by Stephens and Rago for more details.
The optional arguments have defaults as per daemonize_wait, below.
By default, output sent to stdout and stderr after daemonization will be silently
eaten. This behaviour may be adjusted by using redirect_stdout and
redirect_stderr. See the documentation for daemonize_wait below.
Failure if fork was unsuccessful.
daemonize_wait makes the executing process a daemon, but delays full detachment
from the calling shell/process until the returned "release" closure is called.
Any output to stdout/stderr before the "release" closure is called will get
sent out normally. After "release" is called, stdin is connected to /dev/null,
and stdout and stderr are connected as specified by redirect_stdout and
redirect_stderr. The default is the usual behaviour whereby both of these
descriptors are connected to /dev/null.
Note that calling release will adjust SIGPIPE handling, so you should not rely on
the delivery of this signal during this time.
daemonize_wait allows you to daemonize and then start async, but still have
stdout/stderr go to the controlling terminal during startup. By default, when you
daemonize, toplevel exceptions during startup would get sent to /dev/null. With
daemonize_wait, toplevel exceptions can go to the terminal until you call release.
Failure if fork was unsuccessful.