fs.access is not reliable in windows7

[leftstick]

• Version:
  v6.3.0
• Platform:
  64-bit (Windows 7)

When performing following code:

var fs = require('fs');

fs.access('C:/Windows/System32/drivers/etc/hosts', fs.F_OK, function(err) {
    console.log('err', err); //err null
});

I am pretty sure i don't have write permission to the hosts file. But it resolves null to err.

Am i wrong with the usage?

[bnoordhuis]

From the documentation:

fs.F_OK - File is visible to the calling process.

You probably want:

fs.W_OK - File can be written by the calling process.

Good luck.

[leftstick]

@bnoordhuis , when switch to fs.W_OK, still have nothing to err

fs.access('C:/Windows/System32/drivers/etc/hosts', fs.W_OK, function(err) {
    console.log('err', err); //err null
});

but according to following screenshot, i don't have right to write this file

[bnoordhuis]

Node isn't aware of ACLs, it just looks at the file attributes. If the file doesn't have the read-only attribute set, it's considered writable.

[leftstick]

@bnoordhuis So, you mean there is no way to check ACL on windows? A stable way?

[leftstick]

Cause when i trying to write something into the hosts file, error thrown:

var fs = require('fs');

fs.access('C:/Windows/System32/drivers/etc/hosts', fs.W_OK, function(err) {
    console.log('err', err); //err null
});

fs.writeFile('C:/Windows/System32/drivers/etc/hosts', 'test', function(err) {
    console.log(err);//error occurs
});

[bnoordhuis]

you mean there is no way to check ACL on windows?

Not with node core. Maybe with a npm module.

Cause when i trying to write something into the hosts file, error thrown

That's how it should be. Look up 'TOCTOU'. Check-then-write is an anti-pattern.

[leftstick]

Thanks for your time