Node.js OS Module Flashcards for Interviews & Practice

Prepare for Node.js interviews and strengthen your backend development skills with this comprehensive flashcard set focused on the Node.js OS module. Designed for developers ranging from intermediate to senior levels, this collection covers both theoretical concepts and practical applications commonly encountered in production systems. The set explores essential OS module APIs, including system architecture detection, CPU information retrieval, memory monitoring, process scheduling, operating system identification, network interface inspection, uptime tracking, temporary directory management, and user environment information. You'll also learn how to work with operating system constants, error codes, signals, scheduling priorities, platform-specific behaviors, and libuv integrations. Topics include os.arch(), os.platform(), os.type(), os.release(), os.version(), os.cpus(), os.availableParallelism(), os.totalmem(), os.freemem(), os.loadavg(), os.networkInterfaces(), os.hostname(), os.homedir(), os.tmpdir(), os.userInfo(), os.endianness(), os.machine(), os.uptime(), process priorities, signal handling, POSIX error codes, Windows-specific errors, and dlopen constants. Beyond API knowledge, the cards emphasize real-world scenarios such as building monitoring tools, collecting server diagnostics, optimizing containerized applications, implementing health checks, capacity planning, performance analysis, environment detection, and cross-platform application development. Whether you are preparing for technical interviews, reviewing Node.js fundamentals, onboarding new team members, or improving your understanding of operating system interactions in JavaScript applications, this flashcard set provides a structured and efficient learning path. Ideal for Node.js developers, backend engineers, full-stack developers, technical leads, and software architects seeking deeper knowledge of system-level programming concepts within the Node.js ecosystem. You may also be interested in: Master Node.js: From Basics to Production Node.js Stream Module Node.js Cluster Module Node.js Child Process Module Node.js Buffer API Interview Questions Node.js Crypto Module Node.js File System Module

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The node:os module provides operating system-related utility methods and properties.

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os.EOL

<string> The operating system-specific end-of-line marker.

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os.availableParallelism()

This function is a small wrapper about libuv's uv_available_parallelism().

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os.arch()

The return value is equivalent to process.arch.

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os.constants

<Object> Contains commonly used operating system-specific constants for error codes, process signals, and so on.

The specific constants defined are described in OS constants.

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os.cpus()

Returns an array of objects containing information about each logical CPU core.

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os.devNull

<string> The platform-specific file path of the null device.

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os.endianness()

Returns: <string> Returns a string identifying the endianness of the CPU for which the Node.js binary was compiled. Possible values are 'BE' for big endian and 'LE' for little endian.

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os.freemem()

Returns: <integer> Returns the amount of free system memory in bytes as an integer.

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os.getPriority([pid])

Returns the scheduling priority for the process specified by pid.

If pid is not provided or is 0, the priority of the current process is returned.

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os.homedir()

Returns: <string> Returns the string path of the current user's home directory. On POSIX, it uses the $HOME environment variable if defined. Otherwise it uses the effective UID to look up the user's home directory.

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os.hostname()

Returns: <string> Returns the host name of the operating system as a string.

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os.loadavg()

Returns: <number[]> Returns an array containing the 1, 5, and 15 minute load averages. The load average is a measure of system activity calculated by the operating system and expressed as a fractional number.

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os.machine()

Returns: <string> Returns the machine type as a string, such as arm, arm64, aarch64, mips, mips64, ppc64, ppc64le, s390, s390x, i386, i686, x86_64.

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os.networkInterfaces()

Returns: <Object> Returns an object containing network interfaces that have been assigned a network address. Each key on the returned object identifies a network interface. The associated value is an array of objects that each describe an assigned network address. eslint-skip

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os.platform()

Returns: <string> Returns a string identifying the operating system platform for which the Node.js binary was compiled. The value is set at compile time. Possible values are 'aix', 'darwin', 'freebsd','linux', 'openbsd', 'sunos', and 'win32'.

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os.release()

Returns: <string> Returns the operating system as a string. On POSIX systems, the operating system release is determined by calling uname(3). On Windows, GetVersionExW() is used. See https://en.wikipedia.org/wiki/Uname#Examples for more information.

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os.setPriority([pid, ]priority)

pid <integer> The process ID to set scheduling priority for. Default: 0. priority <integer> The scheduling priority to assign to the process.

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os.tmpdir()

Returns: <string> Returns the operating system's default directory for temporary files as a string.

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os.totalmem()

Returns: <integer> Returns the total amount of system memory in bytes as an integer.

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os.type()

Returns: <string> Returns the operating system name as returned by uname(3). For example, it returns 'Linux' on Linux, 'Darwin' on macOS, and 'Windows_NT' on Windows.

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os.uptime()

Returns: <integer> Returns the system uptime in number of seconds.

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os.userInfo([options])

options <Object> encoding <string> Character encoding used to interpret resulting strings. If encoding is set to 'buffer', the username, shell, and homedir values will be Buffer instances. Default: 'utf8'.

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os.version()

Returns: <string> Returns a string identifying the kernel version.

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OS constants

The following constants are exported by os.constants. Not all constants will be available on every operating system.

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Signal constants

History Version Changes v5.11.0 Added support for SIGINFO. The following signal constants are exported by os.constants.signals. Constant Description

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Error constants

The following error constants are exported by os.constants.errno.

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POSIX error constants

Constant Description

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Windows-specific error constants

The following error codes are specific to the Windows operating system. Constant Description

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dlopen constants

If available on the operating system, the following constants are exported in os.constants.dlopen. See dlopen(3) for detailed information. Constant Description

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Priority constants

The following process scheduling constants are exported by os.constants.priority. Constant Description

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libuv constants

Constant Description

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