CODEWITHSUNDEEP
javascriptnode.jsfile-io
Kaspt
Kaspt

Reputation: 55

How to read a specific part of a text file with nodejs

I want to read a text file line by line with nodejs. This works fine with a readable stream. The problem is a other program adds lines to the file. I just want to read the new lines or changes and not the hole file. I Tried it with the functions to move the cursor. But this works only with a writable stream. Is there a possibility to resume the stream after the 'end' event occurs? Or how I can read just a few lines at a specific position of a File? 

var readableStream = fs.createReadStream('file.txt');
var data = '';

readableStream.on('data', function(chunk) {
    data+=chunk;
});

readableStream.on('end', function() {
    console.log(data);
});

It work also fine with the readline core module. But how I can read a single line from a file.

Upvotes: 3

Views: 1394

Answers (2)

mbrandau
mbrandau

Reputation: 554

My way of doing this would be to save the last position and skip those bytes on the next read with stream-skip

Upvotes: 0

Ankit Agarwal
Ankit Agarwal

Reputation: 30739

The filestream library has a watch function which you can use to watch changes in a file. The function executes when there are changes in the file either from nodejs or from external source.

fs.watch('pathToDirectory', function (event, filename) {
    console.log('event is: ' + event);
    if (filename) {
        console.log('filename provided: ' + filename);
    } else {
        console.log('filename not provided');
    }
});

You can read further fs.watch() to know more about this. This is what you should use to achieve what you are asking.

Upvotes: 2

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