/**
* Copyright © 2015 Mattias Andrée <maandree@member.fsf.org>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
/**
* Leave all opened files open.
*/
#define DAEMONISE_NO_CLOSE 1
/**
* Leave all signal handlers rather than
* appling default signal handlers.
*/
#define DAEMONISE_NO_SIG_DFL 2
/**
* Leave the signal block mask as-is.
*/
#define DAEMONISE_KEEP_SIGMASK 4
/**
* Do not remove malformatted environment entries.
*/
#define DAEMONISE_KEEP_ENVIRON 8
/**
* Do not set umask to zero.
*/
#define DAEMONISE_KEEP_UMASK 16
/**
* Do not create a PID file.
*
* Cannot be combined with `DAEMONISE_NEW_PID`.
*/
#define DAEMONISE_NO_PID_FILE 32
/**
* Do not close stderr even if it is
* a terminal device.
*
* Cannot be combined with `DAEMONISE_CLOSE_STDERR`.
*/
#define DAEMONISE_KEEP_STDERR 64
/**
* Close stderr even if it is
* not a terminal device.
*
* Cannot be combined with `DAEMONISE_KEEP_STDERR`.
*/
#define DAEMONISE_CLOSE_STDERR 128
/**
* Do not close stdin.
*/
#define DAEMONISE_KEEP_STDIN 256
/**
* Do not close stdout.
*/
#define DAEMONISE_KEEP_STDOUT 512
/**
* Enables you to select additional
* file descritors to keep open.
*/
#define DAEMONISE_KEEP_FDS 1024
/**
* Override the PID file if it already exists,
* rather than failing. It is a bad idea to do
* this unless you already made sure that the
* daemon is not already running.
*
* Cannot be combined with `DAEMONISE_NO_PID_FILE`.
*/
#define DAEMONISE_NEW_PID 2048
/**
* Daemonise the process. This means to:
*
* - close all file descritors except for those to
* stdin, stdout, and stderr,
*
* - remove all custom signal handlers, and apply
* the default handlers.
*
* - unblock all signals,
*
* - remove all malformatted entries in the
* environment (this not containing an '=',)
*
* - set the umask to zero, to be ensure that all
* file permissions are set as specified,
*
* - change directory to '/', to ensure that the
* process does not block any mountpoint from being
* unmounted,
*
* - fork to become a background process,
*
* - temporarily become a session leader to ensure
* that the process does not have a controlling
* terminal.
*
* - fork again to become a child of the daemon
* supervisor, (subreaper could however be in the
* say, so one should not merely rely on this when
* writing a daemon supervisor,) (the first child
* shall exit after this,)
*
* - create, exclusively, a PID file to stop the daemon
* to be being run twice concurrently, and to let
* the daemon supervicer know the process ID of the
* daemon,
*
* - redirect stdin and stdout to /dev/null,
* as well as stderr if it is currently directed
* to a terminal, and
*
* - exit in the original process to let the daemon
* supervisor know that the daemon has been
* initialised.
*
* Before calling this function, you should remove any
* environment variable that could negatively impact
* the runtime of the process.
*
* After calling this function, you should remove
* unnecessary privileges.
*
* Do not try do continue the process in failure unless
* you make sure to only do this in the original process.
* But not that things will not necessarily be as when
* you make the function call. The process can have become
* partially deamonised.
*
* If $XDG_RUNTIME_DIR is set and is not empty, its value
* should be used instead of /run for the runtime data-files
* directory, in which the PID file is stored.
*
* @etymology (Daemonise) the process!
*
* @param name The name of the daemon. Use a hardcoded value,
* not the process name. Must not be `NULL`.
* @param flags Flags to modify the behaviour of the function.
* A bitwise OR combination of the constants:
* - `DAEMONISE_NO_CLOSE`
* - `DAEMONISE_NO_SIG_DFL`
* - `DAEMONISE_KEEP_SIGMASK`
* - `DAEMONISE_KEEP_ENVIRON`
* - `DAEMONISE_KEEP_UMASK`
* - `DAEMONISE_NO_PID_FILE`
* - `DAEMONISE_KEEP_STDERR`
* - `DAEMONISE_CLOSE_STDERR`
* - `DAEMONISE_KEEP_STDIN`
* - `DAEMONISE_KEEP_STDOUT`
* - `DAEMONISE_KEEP_FDS`
* - `DAEMONISE_NEW_PID`
* @param ... Enabled if `DAEMONISE_KEEP_FDS` is used,
* do not add anything if `DAEMONISE_KEEP_FDS`
* is unused. This is a `-1`-terminated list
* of file descritors to keep open. 0, 1, and 2
* are implied by `DAEMONISE_KEEP_STDIN`,
* `DAEMONISE_KEEP_STDOUT`, and `DAEMONISE_KEEP_STDERR`,
* respectively. All arguments are of type `int`.
* @return Zero on success, -1 on error.
*
* @throws EEXIST The PID file already exists on the system.
* Unless your daemon supervisor removs old
* PID files, this could mean that the daemon
* has exited without removing the PID file.
* @throws EINVAL `flags` contains an unsupported bit, both
* `DAEMONISE_KEEP_STDERR` and `DAEMONISE_CLOSE_STDERR`
* are set, both `DAEMONISE_NO_PID_FILE` and
* `DAEMONISE_NEW_PID`, or both `DAEMONISE_CLOSE_STDERR`
* and `DAEMONISE_KEEP_FDS` are set whilst `2` is
* in the list of file descriptor not to close.
* @throws Any error specified for signal(3).
* @throws Any error specified for sigemptyset(3).
* @throws Any error specified for sigprocmask(3).
* @throws Any error specified for chdir(3).
* @throws Any error specified for pipe(3).
* @throws Any error specified for dup(3).
* @throws Any error specified for dup2(3).
* @throws Any error specified for fork(3).
* @throws Any error specified for setsid(3).
* @throws Any error specified for open(3).
* @throws Any error specified for malloc(3).
*
* @since Always.
*/
int daemonise(const char* name, int flags, ...);
/**
* Remove the PID file created by `daemonise`. This shall
* always be called before exiting after calling `daemonise`,
* even if it failed.
*
* This is a slibc extension.
*
* @etymology (Un)link PID file created by `(daemonise)`!
*
* @return Zero on success, -1 on error.
*
* @throws Any error specified for unlink(3).
*
* @since Always.
*/
int undaemonise(void);
