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DAEMON(3)	       FreeBSD Library Functions Manual		     DAEMON(3)

NAME
     daemon -- run in the background

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <stdlib.h>

     int
     daemon(int	nochdir, int noclose);

     int
     daemonfd(int chdirfd, int nullfd);

DESCRIPTION
     The daemon() function is for programs wishing to detach themselves	from
     the controlling terminal and run in the background	as system daemons.

     Unless the	argument nochdir is non-zero, daemon() changes the current
     working directory to the root (/).

     Unless the	argument noclose is non-zero, daemon() will redirect standard
     input, standard output, and standard error	to /dev/null.

     The daemonfd() function is	equivalent to the daemon() function except
     that arguments are	the descriptors	for the	current	working	directory and
     to	the descriptor to /dev/null.

     If	chdirfd	is equal to (-1) the current working directory is not changed.

     If	nullfd is equals to (-1) the redirection of standard input, standard
     output, and standard error	is not closed.

RETURN VALUES
     The daemon() and daemonfd() functions return the value 0 if successful;
     otherwise the value -1 is returned	and the	global variable	errno is set
     to	indicate the error.

ERRORS
     The daemon() and daemonfd() function may fail and set errno for any of
     the errors	specified for the library functions fork(2) open(2,) and
     setsid(2).

SEE ALSO
     fork(2), setsid(2), sigaction(2)

HISTORY
     The daemon() function first appeared in 4.4BSD.  The daemonfd() function
     first appeared in FreeBSD 12.0.

CAVEATS
     Unless the	noclose	argument is non-zero, daemon() will close the first
     three file	descriptors and	redirect them to /dev/null.  Normally, these
     correspond	to standard input, standard output, and	standard error.	 How-
     ever, if any of those file	descriptors refer to something else, they will
     still be closed, resulting	in incorrect behavior of the calling program.
     This can happen if	any of standard	input, standard	output,	or standard
     error have	been closed before the program was run.	 Programs using
     daemon() should therefore either call daemon() before opening any files
     or	sockets, or verify that	any file descriptors obtained have values
     greater than 2.

     The daemon() function temporarily ignores SIGHUP while calling setsid(2)
     to	prevent	a parent session group leader's	calls to fork(2) and then
     _exit(2) from prematurely terminating the child process.

FreeBSD	Ports 11.2	       December	23, 2017	    FreeBSD Ports 11.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | CAVEATS

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