不熟悉的 Linux API

1. daemon

    #inlcude <unistd.h>

    int daemon(int nochdir, int noclose);

    The daemon() function is for programs wishing to detach themselves from the controlling terminal and run in the background as system daemons.       If nochdir is zero, daemon() changes the calling process's current       working directory to the root directory ("/"); otherwise, the current       working directory is left unchanged.       If noclose is zero, daemon() redirects standard input, standard       output and standard error to /dev/null; otherwise, no changes are       made to these file descriptors.

(This function forks, and if the fork(2) succeeds, the parent calls       _exit(2), so that further errors are seen by the child only.)  On       success daemon() returns zero.  If an error occurs, daemon() returns       -1 and sets errno to any of the errors specified for the fork(2) and       setsid(2).

创建新进程，父进程退出

http://man7.org/linux/man-pages/man3/daemon.3.html

2. 

sched_setscheduler

sched_getscheduler

3. sigaction