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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);

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.

RETURN VALUES
     The daemon() function returns 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() function may fail and	set errno for any of the errors	speci-
     fied for the library functions fork(2) and	setsid(2).

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

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

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	10.1			 June 9, 1993			  FreeBSD 10.1

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

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