The OS Module in Node.js

1. Basic System Information

• os.arch(): CPU architecture (arm, x64, ia32, etc.).
• os.machine(): Machine type (arm64, mips, x86_64, etc.).
• os.endianness(): CPU endianness ('LE' or 'BE').
• os.platform(): Operating system platform (linux, win32, darwin, etc.).
• os.type(): OS name (Linux, Darwin, Windows_NT).
• os.release(): OS release version.
• os.version(): Kernel version.

2. CPU and Parallelism

• os.cpus(): Detailed information about each CPU core.
• os.availableParallelism(): Recommended number of parallel threads.

3. Memory and Resources

• os.freemem(): Free system memory.
• os.totalmem(): Total system memory.
• os.loadavg(): System load averages (Unix only).
• os.uptime(): System uptime in seconds.

4. Paths and Files

• os.homedir(): Current user's home directory.
• os.tmpdir(): Default temporary file directory.
• os.devNull: Null device path (\\.\nul on Windows, /dev/null on POSIX).
• os.EOL: End-of-line marker (\\n on POSIX, \\r\\n on Windows).

5. User Information

• os.userInfo(): Current user details (username, uid, gid, shell, homedir).
• os.hostname(): Hostname of the system.

6. Networking

os.networkInterfaces() returns a list of network interfaces and their assigned IP addresses.

{
  lo: [
    { address: '127.0.0.1', family: 'IPv4', internal: true },
    { address: '::1', family: 'IPv6', internal: true }
  ],
  eth0: [
    { address: '192.168.1.108', family: 'IPv4', internal: false },
    { address: 'fe80::a00:27ff:fe4e:66a1', family: 'IPv6', internal: false }
  ]
}

7. Process Priority

• os.getPriority([pid]): Get process priority.
• os.setPriority([pid, priority]): Set process priority.

Values range from -20 (highest) to 19 (lowest), mapped to constants in os.constants.priority.

8. System Constants

• Signal constants: e.g., SIGINT (Ctrl+C), SIGTERM (terminate), SIGKILL (immediate kill).
• Error constants: POSIX errors (ENOENT, EACCES, ECONNREFUSED) and Windows-specific errors (WSAECONNRESET, WSAETIMEDOUT).
• dlopen constants: Dynamic loading flags like RTLD_LAZY and RTLD_NOW.

Conclusion

The os module in Node.js is a powerful tool for accessing operating system information. It allows developers to adapt applications to hardware and software conditions, manage resources, and understand system behavior more effectively.