So i am using exec to open a shell and run a shell command for me which is:

因此，我使用EXEC打开一个外壳，并为我运行一个外壳命令：

exec('del filename & exit')

Using exit to close the Shell

使用退出关闭外壳

I have to use this exec multiple times in a single run, i have not been able to find what happens to the child process once it goes to exit and closes the CMD, does the child process close itself as soon as the command is completed or do i have to explicitly close the child process

我必须在一次运行中多次使用此EXEC，我还无法查找子进程退出并关闭CMD后会发生什么，子进程是在命令完成后立即自行关闭还是必须显式关闭子进程

UNIX exec (POSIX system call)

Unix EXEC(POSIX系统调用)

There is no child process involved in the picture.

图片中没有涉及任何子进程。

Per the linux man pages,

根据Linux手册页，

One sometimes sees execve() (and the related functions described
in exec(3)) described as "executing a new process" (or similar).
This is a highly misleading description: there is no new process;
many attributes of the calling process remain unchanged (in
particular, its PID). All that execve() does is arrange for an
existing process (the calling process) to execute a new program.

Instead, the exec() family of functions replaces the current process image with a new process image. see: man pages

相反，exec()系列函数用新的进程映像替换当前的进程映像。请参阅：手册页

Node.js exec (Child process module)

Node.js exec(子进程模块)

Unlike the POSIX exec, this function DOES spawn a new process.

与POSIX EXEC不同，该函数确实会产生一个新进程。

Per the docs,

根据医生的说法，

Unlike the exec(3) POSIX system call, child_process.exec() does not replace the existing process and uses a shell to execute the command.

To answer your question,

为了回答你的问题，

does the child process close itself as soon as the command is completed or do i have to explicitly close the child process

The child process is expected to be terminated automatically by the ChildProcess instance, but there is no guarantee that the process will terminate at all costs.

该子进程预计将由ChildProcess实例自动终止，但不能保证该进程将不惜一切代价终止。

Per docs, several events are emitted upon resolution of a child process,

对于每个文档，在解析子进程时发出几个事件，

1. Event 'exit':

When the 'exit' event is triggered, child process stdio streams might still be open.

当‘Exit’事件被触发时，子进程Stdio Streams可能仍处于打开状态。

child.on('exit', (code) => {
   console.log(`child process exited with code ${code}`);
}); 

Note that, the 'exit' event may or may not fire after an error has occurred. When listening to both the 'exit' and 'error' events, guard against accidentally invoking handler functions multiple times.

请注意，在发生错误后，‘Exit’事件可能会触发，也可能不会触发。同时侦听‘Exit’和‘Error’事件时，要防止多次意外调用处理程序函数。

2. Event 'error':

The 'error' event is emitted whenever:

每当出现以下情况时，都会发出‘Error’事件：

• The process could not be spawned.


• The process could not be killed.


• Sending a message to the child process failed.


• The child process was aborted via the signal option.

child.on('error', (err) => {
// This will be called with err being an AbortError if the controller aborts
});

3. Event 'close':

The 'close' event is emitted after a process has ended and the stdio streams of a child process have been closed. This is distinct from the 'exit' event, since multiple processes might share the same stdio streams. The 'close' event will always emit after 'exit' was already emitted, or 'error' if the child failed to spawn.

‘Close’事件在进程结束并且子进程的Stdio流已关闭后发出。这与‘Exit’事件不同，因为多个进程可能共享相同的Stdio流。“Close”事件将始终在“Exit”已发出后发出，如果子级未能派生，则将发出“Error”。

Additionally, a timeout option and a killSignal can be specified to a process for it to be killed by the Node.js runtime using the specified signal if it does not exit in the specified timeout period.

此外，如果进程没有在指定的超时周期内退出，则可以为进程指定一个超时选项和一个KillSignal，以便Node.js运行时使用指定的信号终止该进程。

If timeout is greater than 0, the parent will send the signal identified by the killSignal property (the default is 'SIGTERM') if the child runs longer than timeout milliseconds.

如果超时大于0，并且子进程运行的时间超过超时毫秒，则父进程将发送KILL Signal属性标识的信号(默认为‘SIGTERM’)。

You can pass these options as the 2nd parameter to the exec method as follows:

您可以将这些选项作为第二个参数传递给exec方法，如下所示：

child_process.exec('del filename', {
   timeout: 1000, //milliseconds
   killSignal: "SIGINT"  //POSIX signal name
});

Final note on these handlers:

关于这些处理程序的最后注意事项：

Node.js establishes signal handlers for SIGINT and SIGTERM and Node.js processes will not terminate immediately due to receipt of those signals. Rather, Node.js will perform a sequence of cleanup actions and then will re-raise the handled signal.