Command Line Options | Node.js v6.11.3 Documentation

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# Command Line Options#

Node.js comes with a variety of CLI options. These options expose built-in debugging, multiple ways to execute scripts, and other helpful runtime options.

To view this documentation as a manual page in your terminal, run `man node`.

## Synopsis#

`node [options] [v8 options] [script.js | -e "script"] [--] [arguments]`

`node debug [script.js | -e "script" | <host>:<port>] …`

`node --v8-options`

Execute without arguments to start the REPL.

For more info about `node debug`, please see the debugger documentation.

## Options#

### `-v`, `--version`#

Added in: v0.1.3

Print node's version.

### `-h`, `--help`#

Added in: v0.1.3

Print node command line options. The output of this option is less detailed than this document.

### `-e`, `--eval "script"`#

Added in: v0.5.2

Evaluate the following argument as JavaScript. The modules which are predefined in the REPL can also be used in `script`.

### `-p`, `--print "script"`#

Added in: v0.6.4

Identical to `-e` but prints the result.

### `-c`, `--check`#

Added in: v5.0.0

Syntax check the script without executing.

### `-i`, `--interactive`#

Added in: v0.7.7

Opens the REPL even if stdin does not appear to be a terminal.

### `-r`, `--require module`#

Added in: v1.6.0

Preload the specified module at startup.

Follows `require()`'s module resolution rules. `module` may be either a path to a file, or a node module name.

### `--no-deprecation`#

Added in: v0.8.0

Silence deprecation warnings.

### `--trace-deprecation`#

Added in: v0.8.0

Print stack traces for deprecations.

### `--throw-deprecation`#

Added in: v0.11.14

Throw errors for deprecations.

### `--no-warnings`#

Added in: v6.0.0

Silence all process warnings (including deprecations).

### `--trace-warnings`#

Added in: v6.0.0

Print stack traces for process warnings (including deprecations).

### `--trace-sync-io`#

Added in: v2.1.0

Prints a stack trace whenever synchronous I/O is detected after the first turn of the event loop.

### `--zero-fill-buffers`#

Added in: v6.0.0

Automatically zero-fills all newly allocated Buffer and SlowBuffer instances.

### `--preserve-symlinks`#

Added in: v6.3.0

Instructs the module loader to preserve symbolic links when resolving and caching modules.

By default, when Node.js loads a module from a path that is symbolically linked to a different on-disk location, Node.js will dereference the link and use the actual on-disk "real path" of the module as both an identifier and as a root path to locate other dependency modules. In most cases, this default behavior is acceptable. However, when using symbolically linked peer dependencies, as illustrated in the example below, the default behavior causes an exception to be thrown if `moduleA` attempts to require `moduleB` as a peer dependency:

    {appDir}
     ├── app
     │   ├── index.js
     │   └── node_modules
     │       ├── moduleA -> {appDir}/moduleA
     │       └── moduleB
     │           ├── index.js
     │           └── package.json
     └── moduleA
         ├── index.js
         └── package.json

The `--preserve-symlinks` command line flag instructs Node.js to use the symlink path for modules as opposed to the real path, allowing symbolically linked peer dependencies to be found.

Note, however, that using `--preserve-symlinks` can have other side effects. Specifically, symbolically linked native modules can fail to load if those are linked from more than one location in the dependency tree (Node.js would see those as two separate modules and would attempt to load the module multiple times, causing an exception to be thrown).

### `--track-heap-objects`#

Added in: v2.4.0

Track heap object allocations for heap snapshots.

### `--prof-process`#

Added in: v6.0.0

Process v8 profiler output generated using the v8 option `--prof`.

### `--v8-options`#

Added in: v0.1.3

Print v8 command line options.

Note: v8 options allow words to be separated by both dashes (`-`) or underscores (`_`).

For example, `--stack-trace-limit` is equivalent to `--stack_trace_limit`.

### `--tls-cipher-list=list`#

Added in: v4.0.0

Specify an alternative default TLS cipher list. (Requires Node.js to be built with crypto support. (Default))

### `--enable-fips`#

Added in: v6.0.0

Enable FIPS-compliant crypto at startup. (Requires Node.js to be built with `./configure --openssl-fips`)

### `--force-fips`#

Added in: v6.0.0

Force FIPS-compliant crypto on startup. (Cannot be disabled from script code.) (Same requirements as `--enable-fips`)

### `--openssl-config=file`#

Added in: v6.9.0

Load an OpenSSL configuration file on startup. Among other uses, this can be used to enable FIPS-compliant crypto if Node.js is built with `./configure --openssl-fips`.

### `--use-openssl-ca`, `--use-bundled-ca`#

Added in: v6.11.0

Use OpenSSL's default CA store or use bundled Mozilla CA store as supplied by current NodeJS version. The default store is selectable at build-time.

Using OpenSSL store allows for external modifications of the store. For most Linux and BSD distributions, this store is maintained by the distribution maintainers and system administrators. OpenSSL CA store location is dependent on configuration of the OpenSSL library but this can be altered at runtime using environmental variables.

The bundled CA store, as supplied by NodeJS, is a snapshot of Mozilla CA store that is fixed at release time. It is identical on all supported platforms.

See `SSL_CERT_DIR` and `SSL_CERT_FILE`.

### `--icu-data-dir=file`#

Added in: v0.11.15

Specify ICU data load path. (overrides `NODE_ICU_DATA`)

### `--`#

Added in: v6.11.0

Indicate the end of node options. Pass the rest of the arguments to the script. If no script filename or eval/print script is supplied prior to this, then the next argument will be used as a script filename.

## Environment Variables#

### `NODE_DEBUG=module[,…]`#

Added in: v0.1.32

`','`-separated list of core modules that should print debug information.

### `NODE_PATH=path[:…]`#

Added in: v0.1.32

`':'`-separated list of directories prefixed to the module search path.

Note: on Windows, this is a `';'`-separated list instead.

### `NODE_DISABLE_COLORS=1`#

Added in: v0.3.0

When set to `1` colors will not be used in the REPL.

### `NODE_ICU_DATA=file`#

Added in: v0.11.15

Data path for ICU (Intl object) data. Will extend linked-in data when compiled with small-icu support.

### `NODE_NO_WARNINGS=1`#

Added in: v6.11.0

When set to `1`, process warnings are silenced.

### `NODE_REPL_HISTORY=file`#

Added in: v3.0.0

Path to the file used to store the persistent REPL history. The default path is `~/.node_repl_history`, which is overridden by this variable. Setting the value to an empty string (`""` or `" "`) disables persistent REPL history.

### `NODE_TTY_UNSAFE_ASYNC=1`#

Added in: 6.4.0

When set to `1`, writes to `stdout` and `stderr` will be non-blocking and asynchronous when outputting to a TTY on platforms which support async stdio. Setting this will void any guarantee that stdio will not be interleaved or dropped at program exit. Use of this mode is not recommended.

### `NODE_EXTRA_CA_CERTS=file`#

When set, the well known "root" CAs (like VeriSign) will be extended with the extra certificates in `file`. The file should consist of one or more trusted certificates in PEM format. A message will be emitted (once) with `process.emitWarning()` if the file is missing or malformed, but any errors are otherwise ignored.

Note that neither the well known nor extra certificates are used when the `ca` options property is explicitly specified for a TLS or HTTPS client or server.

### `OPENSSL_CONF=file`#

Added in: v6.11.0

Load an OpenSSL configuration file on startup. Among other uses, this can be used to enable FIPS-compliant crypto if Node.js is built with `./configure --openssl-fips`.

If the `--openssl-config` command line option is used, the environment variable is ignored.

### `SSL_CERT_DIR=dir`#

If `--use-openssl-ca` is enabled, this overrides and sets OpenSSL's directory containing trusted certificates.

Note: Be aware that unless the child environment is explicitly set, this evironment variable will be inherited by any child processes, and if they use OpenSSL, it may cause them to trust the same CAs as node.

### `SSL_CERT_FILE=file`#

If `--use-openssl-ca` is enabled, this overrides and sets OpenSSL's file containing trusted certificates.

Note: Be aware that unless the child environment is explicitly set, this evironment variable will be inherited by any child processes, and if they use OpenSSL, it may cause them to trust the same CAs as node.