The process.argv property returns an array containing the command-line
arguments passed when the Node.js process was launched. The first element will
be
execPath
. See process.argv0 if access to the original value
of argv[0] is needed. The second element will be the path to the JavaScript
file being executed. The remaining elements will be any additional command-line
arguments.
For example, assuming the following script for process-args.js:
Returns a copy of a section of an array.
For both start and end, a negative index can be used to indicate an offset from the end of the array.
For example, -2 refers to the second to last element of the array.
@param ― start The beginning index of the specified portion of the array.
If start is undefined, then the slice begins at index 0.
@param ― end The end index of the specified portion of the array. This is exclusive of the element at the index 'end'.
If end is undefined, then the slice extends to the end of the array.
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s','world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s','world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stderr with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
constcode=5;
console.error('error #%d', code);
// Prints: error #5, to stderr
console.error('error', code);
// Prints: error 5, to stderr
If formatting elements (e.g. %d) are not found in the first string then
util.inspect() is called on each argument and the
resulting string values are concatenated. See util.format()
for more information.
NodeJS.Process.exit(code?: number | string |null): never
The process.exit() method instructs Node.js to terminate the process
synchronously with an exit status of code. If code is omitted, exit uses
either the 'success' code 0 or the value of process.exitCode if it has been
set. Node.js will not terminate until all the 'exit' event listeners are
called.
To exit with a 'failure' code:
import{ exit }from'node:process';
exit(1);
The shell that executed Node.js should see the exit code as 1.
Calling process.exit() will force the process to exit as quickly as possible
even if there are still asynchronous operations pending that have not yet
completed fully, including I/O operations to process.stdout and process.stderr.
In most situations, it is not actually necessary to call process.exit() explicitly. The Node.js process will exit on its own if there is no additionalwork pending in the event loop. The process.exitCode property can be set to
tell the process which exit code to use when the process exits gracefully.
For instance, the following example illustrates a misuse of the process.exit() method that could lead to data printed to stdout being
truncated and lost:
import{ exit }from'node:process';
// This is an example of what *not* to do:
if(someConditionNotMet()){
printUsageToStdout();
exit(1);
}
The reason this is problematic is because writes to process.stdout in Node.js
are sometimes asynchronous and may occur over multiple ticks of the Node.js
event loop. Calling process.exit(), however, forces the process to exit before those additional writes to stdout can be performed.
Rather than calling process.exit() directly, the code should set the process.exitCode and allow the process to exit naturally by avoiding
scheduling any additional work for the event loop:
import process from'node:process';
// How to properly set the exit code while letting
// the process exit gracefully.
if(someConditionNotMet()){
printUsageToStdout();
process.exitCode =1;
}
If it is necessary to terminate the Node.js process due to an error condition,
throwing an uncaught error and allowing the process to terminate accordingly
is safer than calling process.exit().
In Worker threads, this function stops the current thread rather
than the current process.
@since ― v0.1.13
@param ― code The exit code. For string type, only integer strings (e.g.,'1') are allowed.
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s','world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s','world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s','world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s','world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
description() adds text to help. It works on command(), route(), option(), toggle(), and argument(). After adding described repo, browse, and copilot routes to the app above, gh --help prints:
gh 2.62.0
Work seamlessly with GitHub from the command line.
Usage:
gh [OPTIONS] [COMMAND]
Commands:
pr Manage pull requests
repo Manage repositories
browse Open the repository in the browser
copilot Ask Copilot for help
Options:
-h, --help Print help
-v, --version Print version
Help for a child route lists its own options. For a pr list command with described --state and --limit options and an undescribed --repo option, gh pr list --help prints:
pr list
List pull requests in a repository
Usage:
pr list [OPTIONS]
Options:
--repo, -R <VALUE>
--state <VALUE> Filter by state
--limit, -L <VALUE> Maximum number of pull requests to fetch
-h, --help Print help
Positional arguments get their own section. For a repo clone command with a described repository argument, gh repo clone --help prints:
repo clone
Clone a repository locally
Usage:
repo clone [OPTIONS] <REPOSITORY>
Arguments:
<REPOSITORY> Repository to clone
Options:
-h, --help Print help
Help shows every option value as <VALUE> and does not show schema defaults. If users need to know a default or a format, put it in the description.
method-not-allowed means the route does not support the requested method. See Routes and methods.
unprocessable-content means the input could not become a valid model.
printErrors() prints one line per issue. Unexpected input comes first, then schema issues prefixed with the parameter name. gh pr list --state draft --limit lots bogus prints:
unexpected: `bogus`
state: Invalid option: expected one of "open"|"closed"|"merged"|"all"
limit: Invalid input: expected number, received string
The router reports every issue it finds, not only the first one, so the user can fix them all at once.
To format failures your own way, narrow on code. An unprocessable-content failure has an issues list of Standard Schema issues, each with a message and an optional path. A method-not-allowed failure has the requested method and the allowed methods instead:
The process.argv property returns an array containing the command-line
arguments passed when the Node.js process was launched. The first element will
be
execPath
. See process.argv0 if access to the original value
of argv[0] is needed. The second element will be the path to the JavaScript
file being executed. The remaining elements will be any additional command-line
arguments.
For example, assuming the following script for process-args.js:
Returns a copy of a section of an array.
For both start and end, a negative index can be used to indicate an offset from the end of the array.
For example, -2 refers to the second to last element of the array.
@param ― start The beginning index of the specified portion of the array.
If start is undefined, then the slice begins at index 0.
@param ― end The end index of the specified portion of the array. This is exclusive of the element at the index 'end'.
If end is undefined, then the slice extends to the end of the array.
Calls a defined callback function on each element of an array, and returns an array that contains the results.
@param ― callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
Adds all the elements of an array into a string, separated by the specified separator string.
@param ― separator A string used to separate one element of the array from the next in the resulting string. If omitted, the array elements are separated with a comma.
join(".");
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s','world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s','world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stderr with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
constcode=5;
console.error('error #%d', code);
// Prints: error #5, to stderr
console.error('error', code);
// Prints: error 5, to stderr
If formatting elements (e.g. %d) are not found in the first string then
util.inspect() is called on each argument and the
resulting string values are concatenated. See util.format()
for more information.
NodeJS.Process.exit(code?: number | string |null): never
The process.exit() method instructs Node.js to terminate the process
synchronously with an exit status of code. If code is omitted, exit uses
either the 'success' code 0 or the value of process.exitCode if it has been
set. Node.js will not terminate until all the 'exit' event listeners are
called.
To exit with a 'failure' code:
import{ exit }from'node:process';
exit(1);
The shell that executed Node.js should see the exit code as 1.
Calling process.exit() will force the process to exit as quickly as possible
even if there are still asynchronous operations pending that have not yet
completed fully, including I/O operations to process.stdout and process.stderr.
In most situations, it is not actually necessary to call process.exit() explicitly. The Node.js process will exit on its own if there is no additionalwork pending in the event loop. The process.exitCode property can be set to
tell the process which exit code to use when the process exits gracefully.
For instance, the following example illustrates a misuse of the process.exit() method that could lead to data printed to stdout being
truncated and lost:
import{ exit }from'node:process';
// This is an example of what *not* to do:
if(someConditionNotMet()){
printUsageToStdout();
exit(1);
}
The reason this is problematic is because writes to process.stdout in Node.js
are sometimes asynchronous and may occur over multiple ticks of the Node.js
event loop. Calling process.exit(), however, forces the process to exit before those additional writes to stdout can be performed.
Rather than calling process.exit() directly, the code should set the process.exitCode and allow the process to exit naturally by avoiding
scheduling any additional work for the event loop:
import process from'node:process';
// How to properly set the exit code while letting
// the process exit gracefully.
if(someConditionNotMet()){
printUsageToStdout();
process.exitCode =1;
}
If it is necessary to terminate the Node.js process due to an error condition,
throwing an uncaught error and allowing the process to terminate accordingly
is safer than calling process.exit().
In Worker threads, this function stops the current thread rather
than the current process.
@since ― v0.1.13
@param ― code The exit code. For string type, only integer strings (e.g.,'1') are allowed.