(C++ モジュールの一部として) fork を呼び出す長時間実行プロセス (node.js) があります。これにより、新しいプロセスが node.js プロセスの子として作成されます。ただし、この子プロセスを待機/待機するものは何もないため、終了後もゾンビのままです。
現在のプロセスを親にせずにプロセスを fork() して、終了時にゾンビ状態のままではなく、クリーンアップすることはできますか?
そうでない場合は、子で waitpid を呼び出さず、いつ終了するかを気にしないことをどうにかして示すことができますか?
これらすべてに失敗しても、waitpid を実行できるネイティブ モジュールを作成/検索できますが、次のようになることを確認する必要があります。
ありがとう！
デーモンを作成するために使用するコードを次に示します。コメントは、各ステップが実行 される理由を説明しています。
Status daemon_init(void)
{
pid_t pid;
int fh;
/*-----------------------------------------------------------------------
; From the Unix Programming FAQ (corraborated by Stevens):
;
; 1. 'fork()' so the parent can exit, this returns control to the command
; line or shell invoking your program. This step is required so that
; the new process is guaranteed not to be a process group leader. The
; next step, 'setsid()', fails if you're a process group leader.
;---------------------------------------------------------------------*/
pid = fork();
if (pid == (pid_t)-1)
return retstatus(false,errno,"fork()");
else if (pid != 0) /* parent goes bye bye */
_exit(EXIT_SUCCESS);
/*-------------------------------------------------------------------------
; 2. 'setsid()' to become a process group and session group leader. Since
; a controlling terminal is associated with a session, and this new
; session has not yet acquired a controlling terminal our process now
; has no controlling terminal, which is a Good Thing for daemons.
;
; _Advanced Programming in the Unix Environment_, 2nd Edition, also
; ignores SIGHUP. So adding that here as well.
;-----------------------------------------------------------------------*/
setsid();
set_signal_handler(SIGHUP,SIG_IGN); /* ignore this signal for now */
/*-------------------------------------------------------------------------
; 3. 'fork()' again so the parent, (the session group leader), can exit.
; This means that we, as a non-session group leader, can never regain a
; controlling terminal.
;------------------------------------------------------------------------*/
pid = fork();
if (pid == (pid_t)-1)
return retstatus(false,errno,"fork(2)");
else if (pid != 0) /* parent goes bye bye */
_exit(EXIT_SUCCESS);
/*-------------------------------------------------------------------------
; 4. 'chdir("/")' to ensure that our process doesn't keep any directory in
; use. Failure to do this could make it so that an administrator
; couldn't unmount a filesystem, because it was our current directory.
;
; [Equivalently, we could change to any directory containing files
; important to the daemon's operation.]
;
; I just made sure the name of the script we are using contains the full
; path.
;-------------------------------------------------------------------------*/
chdir("/");
/*-----------------------------------------------------------------------
; 5. 'umask(022)' so that we have complete control over the permissions of
; anything we write. We don't know what umask we may have inherited.
;-----------------------------------------------------------------------*/
umask(022);
/*-----------------------------------------------------------------------
; 6. 'close()' fds 0, 1, and 2. This releases the standard in, out, and
; error we inherited from our parent process. We have no way of knowing
; where these fds might have been redirected to. Note that many daemons
; use 'sysconf()' to determine the limit '_SC_OPEN_MAX'.
; '_SC_OPEN_MAX' tells you the maximun open files/process. Then in a
; loop, the daemon can close all possible file descriptors. You have to
; decide if you need to do this or not. If you think that there might
; be file-descriptors open you should close them, since there's a limit
; on number of concurrent file descriptors.
;
; 7. Establish new open descriptors for stdin, stdout and stderr. Even if
; you don't plan to use them, it is still a good idea to have them
; open. The precise handling of these is a matter of taste; if you
; have a logfile, for example, you might wish to open it as stdout or
; stderr, and open '/dev/null' as stdin; alternatively, you could open
; '/dev/console' as stderr and/or stdout, and '/dev/null' as stdin, or
; any other combination that makes sense for your particular daemon.
;
; We do this here via dup2(), which combines steps 6 & 7.
;------------------------------------------------------------------------*/
fh = open(DEV_NULL,O_RDWR);
if (fh == -1)
return retstatus(false,errno,"open(" DEV_NULL ")");
assert(fh > 2);
dup2(fh,STDIN_FILENO);
dup2(fh,STDOUT_FILENO);
dup2(fh,STDERR_FILENO);
close(fh);
return c_okay;
}
この関数をコンテキストで確認したい場合は、https ://github.com/spc476/syslogintr/blob/master/syslogintr.c で表示できます。