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NetBSD 6.1.5 - man page for daemon (netbsd section 3)

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DAEMON(3)			   BSD 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 ter-
     minal 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
     On return 0 indicates success with -1 indicating error.

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

SEE ALSO
     fork(2), setsid(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 descrip-
     tors and redirect them to /dev/null.  Normally, these correspond to standard input, standard
     output and standard error.  However, 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 make sure to either
     call daemon() before opening any files or sockets or, alternately, verifying that any file
     descriptors obtained have a value greater than 2.

BUGS
     daemon() uses fork() as part of its tty detachment mechanism.  Consequently the process id
     changes when daemon() is invoked.	Processes employing daemon() can not be reliably waited
     upon until daemon() has been invoked.

BSD					September 3, 1999				      BSD
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