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NAMEdaemon —
run in the background
LIBRARYStandard C Library (libc, -lc)SYNOPSIS#include <stdlib.h>
int
int
DESCRIPTIONThedaemon () 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,
Unless the argument noclose is non-zero,
The 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 VALUESThedaemon () 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.
ERRORSThedaemon () 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 ALSOfork(2), setsid(2), sigaction(2)HISTORYThedaemon () function first appeared in
4.4BSD. The daemonfd ()
function first appeared in FreeBSD 12.0.
CAVEATSUnless 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. 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 either call
daemon () before opening any files or sockets, or
verify that any file descriptors obtained have values greater than 2.
The
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