Development osx deamon which runs before user login with xcode

The Command Tool project is enough to start creating a daemon. No special build requirements per se, it just depends on what you want the daemon to do.

The way you write the Mac OS X daemon is very similar to how you would approach it on a regular Unix system. Accordingly, there are several things to keep in mind:

• non-interactive : you don't get direct input from the user, but you should also use something like syslogd
  
  for output, since the process is not connected to the terminal li>
• environment : don't assume it has a specific current directory, path, default permissions or any other environment settings - set these explicitly
• security : make sure that the daemon has the minimum minimum privileges required to perform its function and no more (this is a huge topic in itself).
• signals : you will need to monitor and respond to certain signals as they are commonly used to control a process (for example, SIGHUP
  
  forcing the daemon to reload its config file)

There is some good entry on Unix daemons if you take a look. Stevens' book on Unix is ​​always good.

There is some Mac specific information about daemons , mainly for integration with launchd

.

A typical daemon will do something like the following:

• double-fork to detach from the parent process
• configure process group and effective UID
• install signal handlers
• set file permissions umask
• change directory to working directory
• read config file
• open sockets, etc.
• go into an infinite loop to serve requests

The Wikipedia article has an example of a simple daemon .