Merge branch 'develop' into feature/AddTimeServer_#20
Geoffrey Merck
4 years ago
commit
feb5a95b5c
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/*
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* Copyright (c) 2022 by Geoffrey Merck F4FXL / KC3FRA
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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* Losely based on https://github.com/jirihnidek/daemon/blob/master/src/daemon.c
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*/
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#include <unistd.h>
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#include <cstdlib>
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#include <csignal>
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#include <sys/stat.h>
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#include <cstdio>
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#include <cstring>
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#include <sys/types.h>
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#include <fcntl.h>
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#include <pwd.h>
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#include <sys/file.h>
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#include "Daemon.h"
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#include "Log.h"
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int CDaemon::m_pid_fd = -1;
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std::string CDaemon::m_pidFileName("");
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DAEMONIZE_RESULT CDaemon::daemonise(const std::string& pidFile, const std::string& userName)
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{
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// get user
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struct passwd* user = nullptr;
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if(!userName.empty() && getuid() == 0) {
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user = getpwnam(userName.c_str());
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if(user == nullptr) {
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CLog::logFatal("Failed to get %s user", userName.c_str());
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return DR_FAILURE;
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}
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}
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// Create PID file if needed
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if (!pidFile.empty()) {
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auto tempFd = tryGetLock(pidFile);
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if (tempFd < 0) {
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CLog::logFatal("Failed to acquire lock on pidfile %s : %s", pidFile.c_str(), strerror(errno));
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return DR_PIDFILE_FAILED;
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}
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releaseLock(tempFd, "");
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if(user != nullptr) {
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int res = chown(pidFile.c_str(), user->pw_uid, user->pw_gid);
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if(res != 0) {
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CLog::logFatal("Failed to set ownership of pidfile to user %s : %s", userName.c_str(), strerror(errno));
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return DR_FAILURE;
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}
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}
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}
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// change process ownership
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if(user != nullptr) {
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if(setgid(user->pw_gid) != 0) {
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CLog::logFatal("Failed to set %s GID : %s", userName.c_str(), strerror(errno));
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return DR_FAILURE;
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}
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if(setuid(user->pw_uid) != 0) {
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CLog::logFatal("Failed to set %s UID : %s", userName.c_str(), strerror(errno));
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return DR_FAILURE;
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}
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// Double check it worked (AKA Paranoia)
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if (setuid(0) != -1){
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CLog::logFatal("It's possible to regain root - something is wrong!, exiting");
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return DR_FAILURE;
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}
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}
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pid_t pid = 0;
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/* Fork off the parent process */
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pid = fork();
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/* An error occurred */
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if (pid < 0) {
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CLog::logFatal("Forking failed, exiting");
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return DR_FAILURE;
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}
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/* Success: Let the parent terminate */
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if (pid > 0) {
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return DR_PARENT;
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}
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// On success: The child process becomes session leader
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if (setsid() < 0) {
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CLog::logFatal("Failed to set session id, exiting");
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return DR_FAILURE;
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}
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/* Ignore signal sent from child to parent process */
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signal(SIGCHLD, SIG_IGN);
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#ifdef DOUBLE_FORK
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// Fork off for the second time. Some litterature says it is best to fork 2 times so that the process never can open a terminal.
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// However it messes up systemd, event when unit is set as forking
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pid = fork();
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// An error occurred
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if (pid < 0) {
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CLog::logFatal("Second forking failed, exiting");
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return DR_FAILURE;
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}
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// Success: Let the parent terminate
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if (pid > 0) {
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return DR_PARENT;
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}
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#endif
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// Set new file permissions
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umask(0);
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/* Change the working directory to the root directory */
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/* or another appropriated directory */
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if(chdir("/") != 0) {
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CLog::logFatal("Faild to cd, exiting");
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return DR_FAILURE;
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}
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#ifdef CLOSE_FILE_DESC
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// Close all open file descriptors
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for (int fd = sysconf(_SC_OPEN_MAX); fd > 0; fd--) {
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close(fd);
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}
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// Reopen stdin (fd = 0), stdout (fd = 1), stderr (fd = 2)
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stdin = fopen("/dev/null", "r");
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stdout = fopen("/dev/null", "w+");
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stderr = fopen("/dev/null", "w+");
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#endif
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// Try to write PID of daemon to lockfile
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if (!pidFile.empty())
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{
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m_pid_fd = tryGetLock(pidFile);
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if (m_pid_fd < 0) {
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/* Can't open lockfile */
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return DR_PIDFILE_FAILED;
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}
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if (lockf(m_pid_fd, F_TLOCK, 0) < 0) {
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/* Can't lock file */
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return DR_PIDFILE_FAILED;
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}
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m_pidFileName.assign(pidFile);
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/* Get current PID */
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char str[256];
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sprintf(str, "%d\n", getpid());
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/* Write PID to lockfile */
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write(m_pid_fd, str, strlen(str));
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}
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return DR_CHILD;
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}
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void CDaemon::finalise()
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{
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releaseLock(m_pid_fd, m_pidFileName);
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if(!m_pidFileName.empty()) {
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unlink(m_pidFileName.c_str());
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}
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}
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int CDaemon::tryGetLock( const std::string& file )
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{
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mode_t m = umask( 0 );
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int fd = open( file.c_str(), O_RDWR|O_CREAT, 0640 );
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umask( m );
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if( fd >= 0 && flock( fd, LOCK_EX | LOCK_NB ) < 0 ) {
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close( fd );
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fd = -1;
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}
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return fd;
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}
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void CDaemon::releaseLock(int fd, const std::string& file)
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{
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if( fd < 0 )
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return;
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remove(file.c_str());
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close(fd);
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}
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@ -0,0 +1,41 @@
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/*
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* Copyright (c) 2022 by Geoffrey Merck F4FXL / KC3FRA
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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||||||
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <string>
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enum DAEMONIZE_RESULT
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{
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DR_PARENT,
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DR_CHILD,
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DR_FAILURE,
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DR_PIDFILE_FAILED
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};
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class CDaemon
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{
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public:
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static DAEMONIZE_RESULT daemonise(const std::string& pidFile, const std::string& user);
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static void finalise();
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private:
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static int tryGetLock(const std::string& file);
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static void releaseLock(int fd, const std::string& file);
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static int m_pid_fd;
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static std::string m_pidFileName;
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};
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