gdaemon.h

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//
// Copyright (C) 2017 Graeme Walker
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
// ===
///
/// \file gdaemon.h
///

#ifndef G_DAEMON_H
#define G_DAEMON_H

#include "gdef.h"
#include "gexception.h"
#include "gpidfile.h"
#include "gpath.h"
#include <sys/types.h>
#include <string>

namespace G
{
    class Daemon ;
}

/// \class G::Daemon
/// A static interface for daemonising the calling process. Daemonisation 
/// includes fork()ing, detaching from the controlling terminal, setting the 
/// process umask, etc. The windows implementation does nothing.
/// \see G::Process
/// 
class G::Daemon
{
public:
    G_EXCEPTION( CannotFork , "cannot fork" ) ;

    static void detach() ;
        ///< Detaches from the parent environment.
        ///< This typically involves fork()ing,
        ///< _exit()ing the parent, and calling 
        ///< setsid() in the child.

    static void detach( PidFile & pid_file ) ;
        ///< An overload which allows for a delayed write
        ///< of the new process-id to a file.
        ///< 
        ///< A delayed write is useful for network daemons
        ///< which open a listening port. A second instance
        ///< of the process will fail on startup, and should 
        ///< not overwrite the pid file of the running
        ///< server. In this situation PidFile::commit() 
        ///< should be called just before entering the event 
        ///< loop.
        ///< 
        ///< Throws PidFile::Error on error.

private:
    Daemon() ;
    static void setsid() ;
} ;

#endif