Libc-594.9.4.tar.gz

[apple/libc.git] / gen / daemon.3

diff --git a/gen/daemon.3 b/gen/daemon.3
index 0a95ff8d0f85792f56fa52424abadeb7d8cddc79..cd4931f24922a81112e51027a936febc48ff9480 100644 (file)
--- a/gen/daemon.3
+++ b/gen/daemon.3
@@ -30,7 +30,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\"    @(#)daemon.3    8.1 (Berkeley) 6/9/93
 .\" SUCH DAMAGE.
 .\"
 .\"    @(#)daemon.3    8.1 (Berkeley) 6/9/93

-.\" $FreeBSD: src/lib/libc/gen/daemon.3,v 1.10 2001/10/01 16:08:50 ru Exp $
+.\" $FreeBSD: src/lib/libc/gen/daemon.3,v 1.14 2003/11/10 22:04:51 ghelmer Exp $

 .\"
 .Dd June 9, 1993
 .Dt DAEMON 3
 .\"
 .Dd June 9, 1993
 .Dt DAEMON 3


@@ -49,33 +49,70 @@ The
 .Fn daemon
 function is for programs wishing to detach themselves from the
 controlling terminal and run in the background as system daemons.
 .Fn daemon
 function is for programs wishing to detach themselves from the
 controlling terminal and run in the background as system daemons.

+On Mac OS X, the use of this API is discouraged in favor of using
+.Xr launchd 8 .

 .Pp
 Unless the argument
 .Fa nochdir
 is non-zero,
 .Fn daemon
 .Pp
 Unless the argument
 .Fa nochdir
 is non-zero,
 .Fn daemon

-changes the current working directory to the root (``/'').
+changes the current working directory to the root
+.Pq Pa / .

 .Pp
 Unless the argument
 .Fa noclose
 is non-zero,
 .Fn daemon
 .Pp
 Unless the argument
 .Fa noclose
 is non-zero,
 .Fn daemon

-will redirect standard input, standard output and standard error
-to ``/dev/null''.
+will redirect standard input, standard output, and standard error to
+.Pa /dev/null .
+.Sh RETURN VALUES
+.Rv -std daemon

 .Sh ERRORS
 .Sh ERRORS

-If an error occurs,
+The

 .Fn daemon
 .Fn daemon

-returns -1 and sets the global variable
+function may fail and set

 .Va errno
 .Va errno

-to any of the errors specified for the library functions
+for any of the errors specified for the library functions

 .Xr fork 2
 and
 .Xr setsid 2 .
 .Sh SEE ALSO
 .Xr fork 2 ,
 .Xr fork 2
 and
 .Xr setsid 2 .
 .Sh SEE ALSO
 .Xr fork 2 ,

-.Xr setsid 2
+.Xr setsid 2 ,
+.Xr sigaction 2

 .Sh HISTORY
 The
 .Fn daemon
 function first appeared in
 .Bx 4.4 .
 .Sh HISTORY
 The
 .Fn daemon
 function first appeared in
 .Bx 4.4 .

+.Sh CAVEATS
+Unless the
+.Fa noclose
+argument is non-zero,
+.Fn daemon
+will close the first three file descriptors and redirect them to
+.Pa /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
+.Fn daemon
+should therefore either call
+.Fn daemon
+before opening any files or sockets, or verify that any file
+descriptors obtained have values greater than 2.
+.Pp
+The
+.Fn daemon
+function temporarily ignores
+.Dv SIGHUP
+while calling
+.Xr setsid 2
+to prevent a parent session group leader's calls to
+.Xr fork 2
+and then
+.Xr _exit 2
+from prematurely terminating the child process.