| DAEMON(3) | Library Functions Manual | DAEMON(3) |
daemon — run in
the background
#include
<stdlib.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 the argument nochdir is zero,
daemon() changes the current working directory to
the root (/).
If the argument noclose is zero,
daemon() redirects standard input, standard output
and standard error to /dev/null.
Upon success, daemon() returns 0;
otherwise -1 is returned.
The function daemon() may fail and set
errno for any of the errors specified for the library
functions fork(2) and
setsid(2).
The daemon() function first appeared in
4.4BSD.
If the noclose argument is zero,
daemon() closes the first three file descriptors and
redirects 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.
| May 18, 2016 | OpenBSD-current |