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  4. Read a Text Stream Line by Line with lazylines for Node.js

Read a Text Stream Line by Line with lazylines for Node.js

Axel Rauschmayer user avatar by
Axel Rauschmayer
·
Feb. 29, 12 · Interview
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The new Node.js module “lazylines” allows you to read a text stream, one line at a time, lazily.

 

Examples

The following code reads input from stdin and prepends a number to each line.

    var ll = require("lazylines.js");

    process.stdin.resume();
    var inp = new ll.LineReadStream(process.stdin);
    var count = 1;
    inp.on("line", function (line) {
        console.log(count+": "+ll.chomp(line));
        count++;
    });

There are more examples in the demo/ directory. lazylines is very handy for shell programming. For example, you can implement a script that lets you do the following. 

    # List jpg files, oldest first (-t -r), then wrap
    ls -1 -t -r *.jpg | addlinecounts.js 'mv "{line}" {padi}.jpg' | bash

The above executes commands such as 

    mv "new.jpg" 001.jpg
    mv "newer.jpg" 002.jpg
    mv "newest.jpg" 003.jpg

Installation

    npm install lazylines

Related post

  • Write your shell scripts in JavaScript, via Node.js

 

Node.js Stream (computing)

Published at DZone with permission of Axel Rauschmayer, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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