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.'));
}
});
Solution
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