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@ -21,15 +21,43 @@
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namespace posix {
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namespace {
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void quit(std::string const & message)
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void quit(const std::string & message)
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{
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LOG_ERROR(message);
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throw std::runtime_error(message);
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}
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}
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void fork()
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void fork(const std::string & pidfile)
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{
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// If a PID file is specified, we open the file here, because
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// we can't report errors after the fork operation.
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// When we fork, we close thise file in each of the parent
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// processes.
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// Only in the final child process do we write the PID to the
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// file (and close it).
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std::ofstream pidofs;
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if (! pidfile.empty ())
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{
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int oldpid;
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std::ifstream pidrifs;
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pidrifs.open(pidfile, std::fstream::in);
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if (! pidrifs.fail())
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{
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// Read the PID and send signal 0 to see if the process exists.
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if (pidrifs >> oldpid && oldpid > 1 && kill(oldpid, 0) == 0)
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{
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quit("PID file " + pidfile + " already exists and the PID therein is valid");
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}
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pidrifs.close();
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}
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pidofs.open(pidfile, std::fstream::out | std::fstream::trunc);
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if (pidofs.fail())
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{
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quit("Failed to open specified PID file for writing");
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}
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}
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// Fork the process and have the parent exit. If the process was started
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// from a shell, this returns control to the user. Forking a new process is
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// also a prerequisite for the subsequent call to setsid().
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@ -38,7 +66,7 @@ void fork()
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if (pid > 0)
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{
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// We're in the parent process and need to exit.
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//
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pidofs.close();
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// When the exit() function is used, the program terminates without
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// invoking local variables' destructors. Only global variables are
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// destroyed.
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@ -59,6 +87,7 @@ void fork()
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{
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if (pid > 0)
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{
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pidofs.close();
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exit(0);
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}
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else
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@ -67,6 +96,13 @@ void fork()
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}
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}
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if (! pidofs.fail())
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{
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int pid = ::getpid();
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pidofs << pid << std::endl;
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pidofs.close();
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}
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// Close the standard streams. This decouples the daemon from the terminal
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// that started it.
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close(0);
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