child_process_documentation_highlights

What is a child_process mean?
The child_process module provides four different methods for executing external applications:
All methods are asynchronous. The right method will depend on what you need.

• execFile : Execute an external application, given a set of arguments, and callback with the buffered output after the process exits.
• spawn : Execute an external application, given a set of arguments, and provide a streaming interface for I/O and events for when the process exits.
• exec : Execute one or more commands inside a shell and callback with the buffered output after the process exits.
• fork : Execute a Node module as a separate process, given a set of arguments, provide a streaming and evented interface like spawn, and also set up an interprocess communication (IPC) channel between the parent and child process.
  Synchronous Methods
• execFileSync , execSync , spawnSync : It's same as normal methods but the Synchronous Methods will not return until the child process has fully closed. When a timeout has been encountered and killSignal is sent, the method won't return until the process has completely exited.

1- child_process.spawn()

• child_process.spawn schema :
  child_process.spawn(command , [args] , [options])

1. command : String command that the task needed to ran the process. for example "C:/ffmpeg/bin/ffmpeg.exe"
2. [args] : List of string of arguments that the command will execuite it . for example

const args = [
    '-y',
    '-i', 'http://localhost/live/thotho/index.m3u8',
    '-ss', '00:00:01',
    '-vframes', '1',
    '-vf', 'scale=-2:300',
    'C:/ffmpeg/bin/server/thumbnails/thotho.png'
];

3. [options] : options an Objects
   

Options	Type	Benifts
cwd	String	Current working directory of the child process.
env	Object	Environment key-value pairs. Default: process.env.
argv0	String	Explicitly set the value of argv[0] sent to the child process. This will be set to command if not specified.
stdio	Array or String	Child's stdio configuration. see options.stdio
detached	Boolean	Prepare child to run independently of its parent process. Specific behavior depends on the platform. see options.detached
uid	Number	Sets the user identity of the process. see setuid(2)
gid	Number	Sets the group identity of the process. see setgid(2)
serialization	String	Specify the kind of serialization used for sending messages between processes. Possible values are 'json' and 'advanced'. See Advanced serialization for more details. Default: 'json'.
shell	String	f true, runs command inside of a shell. Uses '/bin/sh' on Unix , and process.env.ComSpec on Windows . A different shell can be specified as a string. see Shell requirements and Default Windows shell. Default: false (no shell).
windowsVerbatimArguments	Boolean	No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to true automatically when shell is specified and is CMD. Default: false.
windowsHide	Boolean	Hide the subprocess console window that would normally be created on Windows systems. Default: false.