split_by_pages.js

'use strict';
/******************************************************************************/
const path = process.argv[2];
const linesPerPage = Number(process.argv[3]);
const splitByPages = Number(process.argv[4]);
if (!path || !linesPerPage || !splitByPages) {
  console.log(
    'Add the file path, lines per page and split by pages numbers, please.');
  process.exit();
}
/******************************************************************************/
const fs = require('fs');

const encoding = 'utf8'; //ascii utf8 utf16le

const rl = require('readline').createInterface({
  input: fs.createReadStream(path, encoding),
  terminal: false,
  historySize: 0
});

let outFile;
let lines = 0;
let page  = 0;
/******************************************************************************/
newPart(page + 1);
/******************************************************************************/
rl.on('line', line => {
  fs.writeSync(outFile, `${line}\n`, null, encoding);
  lines++;
  if (lines === linesPerPage) {
    page++;
    lines = 0;
    if (!(page % splitByPages)) {
      newPart(page + 1);
    }
  }
}).on('close', () => {
  fs.closeSync(outFile);
});
/******************************************************************************/
function newPart(page) {
  if(outFile) {
    fs.closeSync(outFile);
  }
  outFile = fs.openSync(path.replace(/(\.[^.]+)?$/, `.${page}$1`), 'w');
  if (page !== 1) fs.writeSync(outFile, '\uFEFF', null, encoding);
  console.log(page);
}
/******************************************************************************/