Exit Handler¶

See exit codes description for a detailed information about exit codes and the standards for them.

Error display¶

The error output of NodeJS is optimized to display better readable and colorful error messages. You will get this by only including this module once.

Interrupt Signals¶

This comes in two parts. At first a handler will be set which will work on interrupt signals and exit the process with a short message. This will be automatically done by loading the module:

TypeScript

import '@alinex/core'

JavaScript

require('@alinex/core');

Supported signals are:

Interrupt	Signal	Exit Code
1	`SIGHUP`	129
2	`SIGINT`	130
3	`SIGQUIT`	131
6	`SIGABRT`	134
9	`SIGTERM`	143

Not all signals are supported here, they are mapped to 128 + signal number for the exit code.

Managing Uncaught Errors¶

In NodeJS there may be some errors which were thrown and neither catched. This can be from rejected promises or thrown exceptions. The following code at the start of your program will catch them all and send them to the exit handler to make a nice error message and exit.

import core from '@alinex/core';

process.on('uncaughtException', err => core.exit(err, 1));
process.on('unhandledRejection', (err: any) => core.exit(err, 1));

Controlled Exit¶

Use this to manually exit the process with a possible error.

Definition

core.exit(
    err: ExitError | Error | string,
    code: number | string | null
)

It is possible to use the exit method for controlled exit:

TypeScript

import core from '@alinex/core'

// exit with code 100
core.exit(new Error("Command already running, can't be called in parallel!"), 100);

JavaScript

const core = require('@alinex/core');

// exit with code 100
core.exit(new Error("Command already running, can't be called in parallel!"), 100);

This will:

output the error.message
output a possible error.description property
auto set the code if possible
exit the process with the given code

The alinex tools are based on the bash exit codes 0, 1 and 124-143. In addition the codes 3-6 are used for NodeJS system codes and some alinex codes are set in the range 16-120 like:

Code	Description
0	OK - no error
1	General error which should not occur
2	Command parameter problem
3	File system access problem
4	Network problems
5	Service or system access problem
6	No such service or address
124	command times out
125	if a command itself fails
126	Command invoked cannot execute
127	"command not found"
128	Invalid argument to exit
129	`SIGHUP` (Signal 1)
130	`SIGINT` like through `Ctrl`+`C` (Signal 2)
131	`SIGQUIT` (Signal 3)
134	`SIGABRT` or `SIGIOT` (Signal 6)
143	`SIGTERM` (Signal 15)
255	Exit status out of range

ExitError¶

Definition

class ExitError extends Error {
    constructor(
        message: string,
        description?: string,
        code?: number | string
    )
    description?: string
    exit?: number
    code?: string
}

Such errors are used to auto detect the exit code and display a more detailed error message in case of exiting the system with this. Therefore the exit() method explicitly supports the additional fields of this type of Error.

TypeScript

import { exit, ExitError } from '@alinex/core'

const err = new ExitError('Wrong Parameter', 'Only the following parameters are allowed...')
err.exit = 2
exit(err);

JavaScript

const core = require('@alinex/core');

const err = new core.ExitError('Wrong Parameter', 'Only the following parameters are allowed...')
err.exit = 2
core.exit(err);

The exit code will be taken from:

the err.exit field
the err.code name (auto detect for node errors)

This procedure gives you the possibility to define the exit code then the error occurs and throw it first but decide later on other position if you want to give it to the exit handler.

Last update: December 31, 2020