Unanavyotumia faili ya mfumo katika Node?

Question

Accepted Answer

Moduli iliyojengwa **`fs`** inasoma na kuandika faili na folda. Inatoa mitindo mitatu ya API — **promises** (kisasa, ikipendekezwa), **callbacks** (async ya asili) na **sync** (kuzuia) — ili uweze kuchagua inayofaa kwa hali.

## API ya promise (inashauriwa)

```js
import { readFile, writeFile, mkdir, readdir } from "fs/promises";

async function work() {
  const data = await readFile("input.txt", "utf8");     // read (utf8 → string)
  await writeFile("output.txt", "Hello");                // write (overwrites)
  await mkdir("new-dir", { recursive: true });           // create dirs (recursive = mkdir -p)
  const files = await readdir("./");                      // list directory contents
}
```

API ya `fs/promises` inafanya kazi vizuri na async/await — kiwango cha kisasa kwa faili-I/O.

## Vigezo vya callback na sync

```js
import fs from "fs";

fs.readFile("file.txt", "utf8", (err, data) => { ... }); // async callback
const data = fs.readFileSync("file.txt", "utf8");         // SYNC — blocks the event loop!
```

**Onyo:** Mbinu za `*Sync` **zinazuia event loop nzima** hadi operesheni ikamalike. Ni sawa wakati wa kuanza (kupakua config mara moja) lakini inapaswa kuepukwa katika waendeshaji wa ombi — kusoma kuzuia kunaganda ombi zote zilizosama.

## Operesheni za kawaida

```js
await fs.promises.appendFile("log.txt", "new line
"); // append
await fs.promises.unlink("old.txt");                    // delete a file
await fs.promises.rename("a.txt", "b.txt");             // rename/move
const stats = await fs.promises.stat("file.txt");       // metadata (size, mtime)
const exists = fs.existsSync("file.txt");               // check existence
```

## Kwa faili kubwa: tumia streams

```js
// ❌ readFile loads the WHOLE file into memory — bad for huge files
const huge = await readFile("10gb.txt"); // could exhaust memory

// ✅ stream it in chunks (constant memory)
fs.createReadStream("10gb.txt").pipe(fs.createWriteStream("copy.txt"));
```

Kwa faili kubwa, `readFile` inapakua kila kitu katika kumbukumbu mara moja; **streams** huchakata data katika vipande vya kumbukumbu ya kawaida.

## Kwa nini inamaanisha

Faili-I/O ni uwezo wa msingi wa Node kwa upakuaji wa config, kurekodi, upakuaji/kupakua faili, na zana.

Kujua mitindo mitatu ya API — na muhimu, kwamba **mbinu za sync zinazuia event loop** (zizuie katika seva) na kwamba **faili kubwa zinahitaji streams** (si `readFile`) — ni muhimu kwa kuandika msimbo wa kurudisha faili ambayo ni sahihi na wenye utendaji chini ya samaduni.

API ya promise na async/await ni kiwango kinachofanya vizuri kwa matumizi ya kila siku.