os module for system information in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code using os module?

Consider this Node.js code snippet using the os module. What will be the output of the os.platform() call?

Node.js

import os from 'os';
console.log(os.platform());

A "win32" (on Windows), "linux" (on Linux), or "darwin" (on macOS) depending on the OS

B "Windows", "Linux", or "MacOS" as full names

C The CPU architecture like "x64" or "arm"

D The hostname of the computer

💡 Hint

The os.platform() method returns a short string identifying the operating system platform.

The os.platform() method returns a string like "win32", "linux", or "darwin" to identify the OS platform in a short form.

❓ Predict Output

intermediate

What does os.cpus() return?

Given this code snippet, what is the type of the value returned by os.cpus()?

Node.js

import os from 'os';
const cpus = os.cpus();
console.log(typeof cpus);

A "number" representing the count of CPUs

B "string" describing the CPU model

C "object" because it returns an array of CPU info objects

D "undefined" because os.cpus() does not exist

💡 Hint

Check the Node.js os module docs for the return type of os.cpus().

The os.cpus() method returns an array of objects, each describing a CPU core.

❓ component_behavior

advanced

How does os.freemem() behave in a running Node.js app?

If you call os.freemem() multiple times in a Node.js app, what can you expect about the values returned?

A The values always return zero

B The values remain constant during the app lifetime

C The values increase steadily as the app runs

D The values may change over time as memory usage changes

💡 Hint

Think about how free memory changes as programs run.

The free memory reported by os.freemem() can change as the system allocates and frees memory.

📝 Syntax

advanced

Which option correctly imports and uses os.totalmem() in Node.js ES modules?

Choose the correct code snippet to import the os module and log total system memory in bytes.

A

import * as os from 'os';
console.log(os.totalmem());

B

const os = require('os');
console.log(os.totalmem());

C

import { totalmem } from 'os';
console.log(totalmem());

D

import os from 'os';
console.log(os.totalmem());

💡 Hint

Node.js ES modules use import syntax with default or named imports.

In ES modules, import * as os from 'os'; imports the os module as a namespace. Then os.totalmem() calls the function.

🔧 Debug

expert

Why does this code throw TypeError: os.uptime is not a function?

Given this code snippet, why does it throw a TypeError?

Node.js

import { uptime } from 'os';
console.log(os.uptime());

A Because uptime is not a function in the os module

B Because os is not defined; only uptime was imported, so os.uptime() is undefined

C Because import syntax is invalid for os module

D Because uptime requires arguments but none were given

💡 Hint

Check what variables are defined after import.

The code imports only uptime but tries to call os.uptime(). The variable os is not defined, causing the error.

Practice

1. What does the Node.js os module primarily provide?

easy

A. Information about the operating system and hardware

B. Functions to create web servers

C. Tools for database management

D. Methods to handle file uploads

Solution

1. Step 1: Understand the purpose of the os module

   The os module in Node.js is designed to provide details about the operating system and hardware, such as CPU info, memory, and platform.

2. Step 2: Compare with other options

   Options A, C, and D relate to web servers, databases, and file handling, which are not the focus of the os module.

3. Final Answer:

   Information about the operating system and hardware -> Option A

4. Quick Check:

   os module = system info [OK]

Hint: Remember: os module = operating system info [OK]

Common Mistakes:

• Confusing os module with http or fs modules
• Thinking os manages databases or servers

2. Which of the following is the correct way to import the os module in Node.js?

easy

A. require os = 'os';

B. import os from 'os';

C. const os = import('os');

D. const os = require('os');

Solution

1. Step 1: Recall Node.js module import syntax

   In Node.js, the common way to import built-in modules is using const module = require('module-name');.

2. Step 2: Check each option

   const os = require('os'); uses correct syntax. import os from 'os'; is ES module syntax but requires special setup. const os = import('os'); is invalid syntax. require os = 'os'; is incorrect assignment.

3. Final Answer:

   const os = require('os'); -> Option D

4. Quick Check:

   require('os') = correct import [OK]

Hint: Use require('os') to import os module in Node.js [OK]

Common Mistakes:

• Using ES module import without config
• Wrong assignment syntax
• Confusing import() with require()

3. What will the following code output if run on a typical system?

const os = require('os');
console.log(os.cpus().length);

medium

A. The hostname of the system

B. The number of CPU cores on the system

C. The total amount of system memory in bytes

D. An error because cpus is not a function

Solution

1. Step 1: Understand os.cpus() method

   The os.cpus() method returns an array of objects, each representing a CPU core.

2. Step 2: Analyze the code output

   The code logs the length of this array, which equals the number of CPU cores on the system.

3. Final Answer:

   The number of CPU cores on the system -> Option B

4. Quick Check:

   os.cpus().length = CPU cores count [OK]

Hint: os.cpus() returns array of cores; length = core count [OK]

Common Mistakes:

• Thinking it returns memory size
• Assuming it returns hostname
• Believing cpus() is not a function

4. Identify the error in this code snippet:

const os = require('os');
console.log(os.totalmem());

medium

A. No error; it correctly logs total memory

B. totalmem is not a function, should be totalMem

C. Missing parentheses after totalmem

D. Should import os with import statement

Solution

1. Step 1: Check method name correctness

   The correct method to get total memory is os.totalmem() all lowercase, so spelling is correct.

2. Step 2: Verify method usage

   The code uses os.totalmem() correctly with parentheses, so no syntax error.

3. Step 3: Re-examine options

   totalmem is not a function, should be totalMem claims totalMem is correct, but Node.js uses totalmem lowercase. So totalmem is not a function, should be totalMem is incorrect.

4. Step 4: Identify actual error

   There is no error; the code is correct.

5. Final Answer:

   No error; it correctly logs total memory -> Option A

6. Quick Check:

   os.totalmem() = total memory [OK]

Hint: Check exact method names in docs; totalmem is lowercase [OK]

Common Mistakes:

• Capitalizing method names incorrectly
• Forgetting parentheses on function calls
• Confusing import styles

5. You want to write a Node.js script that prints the system's free memory as a percentage of total memory using the os module. Which code snippet correctly does this?

hard

A. const os = require('os');
console.log(`Free memory: ${os.freemem / os.totalmem * 100}%`);

B. const os = require('os');
const free = os.totalmem();
const total = os.freemem();
console.log(`Free memory: ${(free / total * 100).toFixed(2)}%`);

C. const os = require('os');
const free = os.freemem();
const total = os.totalmem();
console.log(`Free memory: ${(free / total * 100).toFixed(2)}%`);

D. const os = require('os');
const free = os.freemem();
const total = os.totalmem();
console.log('Free memory: ' + free + '/' + total + '%');

Solution

1. Step 1: Identify correct methods for free and total memory

   os.freemem() returns free memory, and os.totalmem() returns total memory.

2. Step 2: Calculate percentage and format output

   Divide free by total, multiply by 100, and use toFixed(2) to show two decimals. const os = require('os'); const free = os.freemem(); const total = os.totalmem(); console.log(`Free memory: ${(free / total * 100).toFixed(2)}%`); does this correctly.

3. Step 3: Check other options for errors

   const os = require('os'); const free = os.totalmem(); const total = os.freemem(); console.log(`Free memory: ${(free / total * 100).toFixed(2)}%`); swaps free and total memory, giving wrong result. const os = require('os'); console.log(`Free memory: ${os.freemem / os.totalmem * 100}%`); misses parentheses on functions. const os = require('os'); const free = os.freemem(); const total = os.totalmem(); console.log('Free memory: ' + free + '/' + total + '%'); prints raw numbers without percentage calculation.

4. Final Answer:

   const os = require('os'); const free = os.freemem(); const total = os.totalmem(); console.log(`Free memory: ${(free / total * 100).toFixed(2)}%`); -> Option C

5. Quick Check:

   free/total * 100 with toFixed(2) = correct percentage [OK]

Hint: Divide freemem() by totalmem(), multiply by 100, format decimals [OK]

Common Mistakes:

• Swapping free and total memory values
• Forgetting parentheses on freemem() or totalmem()
• Not formatting output as percentage