CODEWITHSUNDEEP
node.jsreadfilefs
daremkd
daremkd

Reputation: 8424

Does readFile caches the content?

Say I have:

var fs = require('fs');
var a= fs.readFile(__dirname + '/someBigFile.txt', function(err, data) {
    console.log(data);
});

I've noticed that, if it first takes, say, 2 seconds to read someBigFile, now it takes several milliseconds. Is there some internal caching is Node.js happening when you read it multiple times? for example:

for(var i =0; i < 10000; i++)
{
    var greet = fs.readFile(__dirname + '/greet.txt', "utf-8", function(err, data) {
    });
}

Upvotes: 7

Views: 6309

Answers (4)

Константин Ван
Константин Ван

Reputation: 14809

The fs module does not cache what it has read.

But if you need a cached version and you’re (luckily) trying to read JSON files caching, you can use require for that. It does read, and cache.

Upvotes: 0

Hussein Nasser
Hussein Nasser

Reputation: 430

So I ran into this problem but in a different context, I wrote a node js server that reads a text file on a network drive that is essentially a read-only to me, however, another application occasionally writes to that file and I'd like to immediately see these changes. My Node js app kept reading a stale version of the file although I can see the file is changed.

I solved it after reading the help and added an 'rs' which bypasses the system local file cache https://nodejs.org/api/fs.html#fs_file_system_flags

   fs.readFile( path,  {"flag": 'rs'} , (err, data) => {} )

Upvotes: 4

Zeeshan Hassan Memon
Zeeshan Hassan Memon

Reputation: 8325

Simple answer is No - It's not internal caching like in node.js.

But you can wrap fs module in a cached read-only version to speed up things if you're reading the same files and directories multiple times, and things don't change on disc.

Upvotes: 1

VoidVolker
VoidVolker

Reputation: 1029

No. It likely the your storage system cache (in some cases it can be and OS or some additional software cache). Try to write some data to file and try to read it again.

Upvotes: 1

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