Today I decided to clean up and organise files on my windows machine at work. This process involved deleting files I no longer have use for and grouping the rest in folders. So I ended up with folders for audio, video, projects, ebooks, e.t.c.
One of the folders that I opened contained about 50 small mp3 files. Before deleting the files I had to play them just to make sure they didn't contain anything important. What do I know, turns out they are clips of a DHH(the RoR creator) interview - please don't ask me how they got to my computer. He's quite an opinionated guy so I decided to keep the files. But 50 files? Wouldn't it be nice if I could glue them together into a single file? Well, being the hacker that I am I popped open my terminal and started writing a program.
I broke down the task to two main parts.
The first part turned out to be quite easy because the files were named with a date/time stamp in the following format: Mon Jan 03 10;02;07 2011.mp3
. This meant that I could extract the time from the file names and sort them accordingly. To simplify this further I decided to rename the files with an easier format for sorting - for this I created the rename.js
file:
/*
I placed all the audio files in ./files directory
*/
var fs = require('fs'),
files = fs.readdirSync('./files');
files.forEach(function (file) {
var currentname = './files/' + file,
date = parseDate(file),
newname = './files/' + date.split(';').join('') + '.mp3';
renameFile(currentname, newname);
console.log('Renamed ' + currentname + ' to ' + newname);
});
/*
This function renames a file
@param: (String) currentname - current file name
@param: (String) newname - new file name
*/
function renameFile(currentname, newname) {
fs.renameSync(currentname, newname);
}
/*
Extracts date/time from file name string
@param: (String) filename - file name
*/
function parseDate(name) {
var date = name.substring(11, 19);
return date;
}
console.log('Done');
Up next I had to create the main program that combines the files and writes them to a single file. Streams to the rescue!
Streams are a powerful feature in Node.js, they create a transportation system that moves your data in chunks. The source of the data is a readable stream and the destination a writable stream. The file system module has 2 methods that you can use to take advantage of Node streams, fs.createReadStream
and fs.createWriteStream
. I created a new file for the main program, stream.js
var fs = require('fs'),
files = fs.readdirSync('./files'),
clips = [],
stream,
currentfile,
dhh = fs.createWriteStream('./dhh-interview.mp3');
// create an array with filenames (time)
files.forEach(function (file) {
clips.push(file.substring(0, 6));
});
// Sort
clips.sort(function (a, b) {
return a - b;
});
// recursive function
function main() {
if (!clips.length) {
dhh.end("Done");
return;
}
currentfile = './files/' + clips.shift() + '.mp3';
stream = fs.createReadStream(currentfile);
stream.pipe(dhh, {end: false});
stream.on("end", function() {
console.log(currentfile + ' appended');
main();
});
}
main();
That's it. Lastly I needed to run my programs.
node rename.js && node stream.js
Note: I have included a few files in my repo so that you can be able to try this out.