Node.js Exit Codes

Node.js is a cross-platform, open-source back-end JavaScript runtime environment that uses the V8 engine to execute JavaScript code outside of a web browser. Node.js allows developers to utilize JavaScript to create command-line tools and server-side scripting, which involves running scripts on the server before sending the page to the user's browser.

In the following article, we are going to talk about the different exit codes in node.js when exiting a process.

The following is the list of exit codes in Node.js along with its descriptions:

• Exit Code 0: Node.js normally ends with a status code of 0 whenever there are no more open async operations and the code doesn't produce any uncaught exceptions.
• Exit Code 1, Uncaught Fatal Exception: If an uncaught exception occurs and it is not resolved by a domain or a "uncaughtException" event handler, Node.js exits with an exit code of 1.
• Exit Code 2: The exit code 2 is reserved by Bash for abuse of built-in features.
• Exit Code 3, Internal JavaScript Parse Error: When internal code cannot be effectively interpreted, this exit code might be utilised in development. This is highly uncommon and often only occurs while Node.js is being developed.
• Exit Code 4, Internal JavaScript Evaluation Failure: It is also applied in situations where the JavaScript code fails to return the function value during development.
• Exit Code 5, Fatal Error: When a fatal, unrecoverable error occurred in V8, this exit code is utilised. Usually, stderr will produce a message with the prefix FATAL ERROR.
• Exit Code 6, Non-function Internal Exception Handler: When an internal fatal exception handler function is set to a non-function and unable to be invoked, it is helpful.
• Exit Code 7, Internal Exception Handler Run-Time Failure: This error code is used when the internal fatal exception handler code itself issued an error when attempting to handle the uncaught exception. This may occur, for instance, if a domain.on('error') handler or a "uncaughtException" returns an error.
• Exit Code 8: Exit code 8 in earlier versions of Node.js was sometimes used to denote an uncaught error.
• Exit Code 9, Invalid Argument: This is employed when an unspecified option was given or when a value-required option was given without one..
• Exit Code 10, Internal JavaScript Run-Time Failure: When the bootstrapping function was invoked, the JavaScript source code internal to Node.js's bootstrapping procedure threw an error.
• Exit Code 12, Invalid Debug Argument: The ports specified were either unavailable or invalid, yet the —debug, —inspect, and/or —debug-brk options were set.
• Exit Code >128, Signal Exits: Node.js's exit code is 128 plus the signal code's value if it gets a fatal signal like SIGKILL or SIGHUP. This is a common Unix practice since signal exits set the high-order bit before containing the signal code's value and exit codes are often specified as 7-bit integers.

Example 1: The code in the following example terminates without any error, hence an exit code of 0.

console.log("Running...");
process.on('exit', function(code){
    return console.log(`Exiting with code ${code}`);
});

Output:

Example 2: In this example, we will deliberately terminate the following code with exit code 1.

console.log('This code will terminate with exit code 1'); 

process.on('exit', function(code) { 
    return console.log(`Exit Code: ${code}`); 
}); 

setTimeout((function() { 
    return process.exit(1);
}), 5000); 

Output:

Reference: https://nodejs.org/api/process.html#process_exit_codes