CODEWITHSUNDEEP
javascriptnode.jsregex
hussain
hussain

Reputation: 7083

How to print lines that contains specific string?

I want to print lines that contains date in the string , i am using split module to achieve that task. below code is always printing else statement.

ctrl.js

fs.readFile(dir + '/' + logFile, 'utf8', function(err, data) {
        var lines = data.split('\n');
        var linesWithDate = lines.split('|')[0].replace(/[\[\]']+/g,'');
        lines.forEach(function(line) {
            if (linesWithDate) {
                console.log('print lines with date',line);
             } else {
                console.log('print lines without date',line);
             }
        }
    });

file data 

[2017-03-23T18:13:16Z]|zlpv7490|verbose|bmid: n/a|infra.topicWorkers|topology changed, emitting topology event lorem ipsum
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy 
[2017-03-23T19:20:16Z]|zlpv7490|verbose|bmid: n/a|infra.topicWorkers|topology changed, emitting topology event lorem ipsum

Upvotes: 1

Views: 2007

Answers (2)

rsp
rsp

Reputation: 111336

How to print lines that contains specific string?

const split = require('split');
fs.createReadtStream(path.join(dir, logFile), 'utf8')
  .pipe(split()).on('data', (line) => {
    if (line.indexOf('string') > -1) {
        console.log('Line with string:', line);
    } else {
        console.log('Line without string:', line);
    }
});

I want to print lines that contains date in the string , i am using split module to achieve that task. below code is always printing else statement

I don't think you were using the split module. This example does:

const split = require('split');
const regex = require('regex-iso-date');
fs.createReadtStream(path.join(dir, logFile), 'utf8')
  .pipe(split()).on('data', (line) => {
    if (regex().test(line)) {
        console.log('Line with date:', line);
    } else {
        console.log('Line without date:', line);
    }
});

Note that this will not necessarily be a valid date, as it may match dates like 2017-13-13... - to test for valid dates only see this answer:

Or if you want to match for your specific strings like [2017-03-23T18:13:16Z] then you may try something like this:

const split = require('split');
const regex = /\[\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\w+\]/;
fs.createReadtStream(path.join(dir, logFile), 'utf8')
  .pipe(split()).on('data', (line) => {
    if (regex.test(line)) {
        console.log('Line with date:', line);
    } else {
        console.log('Line without date:', line);
    }
});

Note that it will also match invalid dates if you have them in your files.

Upvotes: 1

John Vandivier
John Vandivier

Reputation: 2426

Here is some code which prints out only valid parsed dates by line. I use the readline module instead of readfile, but you should be able to easily adapt the logic by replacing input: process.stdin: 'use strict';

var sExample = '[2017-03-23T18:13:16Z]|zlpv7490|verbose|bmid: n/a|infra.topicWorkers|topology changed, emitting topology event lorem ipsum';

const readline = require('readline');
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.setPrompt('Enter example string to test > ');
rl.prompt();

rl.on('line', (line) => {
  var sCandidate = line.split('|')[0].replace(/[\[\]']+/g,'');

  if (Date.parse(sCandidate)) {                   //it is a valid date
    console.log(sCandidate);
  }

  process.exit(0);
});

Upvotes: 0

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