Different results from asynchronous and synchronous reading

Question

I have a fairly simple script that attempts to read and then parse a JSON file. The JSON is very simple and I am pretty sure it is valid.

{
    "foo": "bar"
}

Now, I have been trying to read it with fs.readFile. When read no errors occur and the returned data is a string. The only problem is that the string is empty.

I repeated my code but used fs.readFileSync, this returned the file perfectly using the same path. Both had a utf-8 encoding specified.

It is very simple code, as you can see.

fs.readFile('./some/path/file.json', 'utf8', function(err, data) {
    if(!err) {
        console.log(data); // Empty string...
    }
});

console.log(fs.readFileSync('./some/path/file.json', 'utf8')); // Displays JSON file

Could it be permissions or ownership? I have tried a permission set of 755 and 777 to no avail.

I am running node v0.4.10. Any suggestions to point me in the right direction will be much appreciated. Thanks.

Edit: Here is a block of my actual code. Hopefully this will give you a better idea.

// Make sure the file is okay
fs.stat(file, function(err, stats) {
    if(!err && stats.isFile()) {
        // It is okay. Now load the file
        fs.readFile(file, 'utf-8', function(readErr, data) {
            if(!readErr && data) {
                // File loaded!
                // Now attempt to parse the config
                try {
                    parsedConfig = JSON.parse(data);
                    self.mergeConfig(parsedConfig);

                    // The config was loaded and merged
                    // We can now call the callback
                    // Pass the error as null
                    callback.call(self, null);

                    // Share the news about the new config
                    self.emit('configLoaded', file, parsedConfig, data);
                }
                catch(e) {
                    callback.call(self, new Error(file + ': The config file is not valid JSON.'));
                }
            }
            else {
                callback.call(self, new Error(file + ': The config file could not be read.'));
            }
        });
    }
    else {
        callback.call(self, new Error(file + ': The config file does not exist.'));
    }
});

Sorry, no it is not, I have just typed up a copy, I shall add UTF-8. — Olical
– Olical, Commented Nov 12, 2011 at 13:58
@thejs I have added a block of my actual code. I can assure you that the file variable is a string and goes to the correct file. — Olical
– Olical, Commented Nov 12, 2011 at 14:01
Could you try utf8 instead of utf-8? Node wants it to be utf8, not sure whether it allows utf-8, too - although it'd be weird not to throw an exception... — thejh
– thejh, Commented Nov 12, 2011 at 14:05
@thejs Done. No difference. I have tried that before too because I noticed it written that way in the docs for writing a file. — Olical
– Olical, Commented Nov 12, 2011 at 14:09

malletjo · Accepted Answer · 2011-11-12 18:39:19Z

1

This is pretty weird.

The code looks.

var fs = require('fs');

fs.readFile('./jsonfile', 'utf8', function(err, data) {
        if(err) {
                console.error(err);
        } else {
                console.log(data);
                parsedConfig = JSON.parse(data);
                console.log(parsedConfig);
                console.log(parsedConfig.foo);
        }
});

Json file:

{
        "foo": "bar"
}

output :

$ node test_node3.js 
{
        "foo": "bar"
}

{ foo: 'bar' }
bar

This is on node 0.4.10 , but i'm pretty sure it should work on all node version.

So why your data is empty ? You should check err in this case (like mine) and post the output if any. If you have no error, you may fill a bug on github

answered Nov 12, 2011 at 18:39

malletjo

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2 Comments

Olical Over a year ago

There is nothing in the error. It thinks it has worked but returns no data. Maybe I should file a bug, but I don't know how I would recreate the problem. I am not really doing anything spectacular, could it be a Mac thing?

malletjo Over a year ago

If you can't recreate it, you can't fill a bug. It may be mac related.

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