내장 모듈 - fs(open, close, read, write)

fs

• 파일시스템과 상호작용 하는 모듈
• 비동기 방식을 기본으로 동작, 동기 메서드도 제공

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file

open

• fs.open(path,flags,mode,callback) => void
  • callback : (err:NodeJS.ErrnoException, fd:number) => void
  • mode : string - w(쓰기), r(읽기), a(추가하기)
• fs.openSync(path,flags,mode) => fd:number
• path : 개방할 파일 경로
• flags
  • r(reading), w(writing), a(appending), ...

close

• fs.close(fd, callback) => void
• fs.closeSync(fd) => void

read

• fs.readSync(fd:number, buffer, offset, length, position) => number
• fs.read(fd, buffer, offset, length, position, callback) => void

write

• fs.writeSync(fd, buffer, offset, position)

e.g. readFileSync, writeFileSync

import fs from "fs";
import { Buffer } from "buffer";

function readFileSync(path: string, bufferSize?: number) {
  const chunks: Buffer[] = [];
  const buffer = Buffer.alloc(bufferSize || 10);
  let position = 0;

  try {
    // open file
    const fd = fs.openSync(path, "r");

    // read file
    while (true) {
      const size = fs.readSync(fd, buffer, 0, buffer.length, position);
      if (size > 0) {
        const chunk = Buffer.alloc(size);
        buffer.copy(chunk, 0, 0, size);
        chunks.push(chunk);
        position += size;
      } else {
        break;
      }
    }
    // close file
    fs.closeSync(fd);

    fs.close();
  } catch (err) {
    console.error(err);
  }

  return Buffer.concat(chunks);
}

function writeFileSync(path: string, data: string, bufferSize?: number) {
  const buffer = Buffer.alloc(bufferSize || 10);
  let start = 0;

  try {
    // open file
    const fd = fs.openSync(path, "w");
    const content = Buffer.from(data);

    // write file
    while (start < content.length) {
      let end = start + buffer.length;
      end = end < content.length ? end : content.length;
      content.copy(buffer, 0, start, end);
      fs.writeSync(fd, buffer, 0, end - start);
      start = end;
    }
    // close file
    fs.closeSync(fd);

    console.log("Completed");
  } catch (err) {
    console.error(err);
  }
}

const buf = readFileSync("files/text.txt");

writeFileSync(
  "files/customWriteFileSync",
  "Hello World\nNice to meet you\nSee you next time."
);