APUEの中に書いてあるdaemonの書き方

Daemon Coding Rules

1. call umask to set file mode creation mask.
2. fork and have parent process exit.

• When invoked as shell command, letting parent exit make the shell think the command is finished
• ensure that the child process is not a process group leader. This is a prerequisite for setsid

1. call setsid

• The child process will be the leader of the new process group
• The child process will be the leader of the new process session
• The child process will be detached from its controlling terminal

1. chdir
2. close files inherited from its parent
3. redirect stdin, stdout, stderr to /dev/null