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move file first string to the end of file: node.js, stream
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#!/usr/bin/env node | |
const fs = require('fs'); | |
const {Buffer} = require('buffer'); | |
const filepath = process.argv[2]; | |
if (!filepath) { | |
console.log('\nДолжен быть указан путь к существующему файлу!\n'); | |
process.exit(0); | |
} | |
console.log(`FILE: ${filepath}`); | |
let buffer; | |
const readStream = fs.createReadStream(filepath);//, {highWaterMark: 7}); | |
readStream.on('error', (err) => { | |
console.error('READING ERROR!!!'); | |
console.trace(err); | |
process.exit(1); | |
}) | |
.on('data', (b) => { | |
buffer = buffer ? Buffer.concat([buffer, b]) : b; | |
readStream.pause(); | |
const pos = buffer.indexOf('\n'); | |
if (pos === -1) { | |
readStream.resume(); | |
return; | |
} | |
const firstLine = buffer.slice(0, pos); | |
const restLine = buffer.slice(pos+1, buffer.length); | |
const writeStream = fs.createWriteStream(filepath, {start: 0, flags: 'a'}); | |
writeStream.on('error', (err) => { | |
console.error('WRITING ERROR!!!'); | |
console.trace(err); | |
process.exit(1); | |
}); | |
readStream.removeAllListeners('data'); | |
readStream.once('end', () => { | |
writeStream.write('\n'); | |
writeStream.end(firstLine); | |
}); | |
writeStream.write(restLine); | |
readStream.pipe(writeStream); | |
}); |
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