CODEWITHSUNDEEP
node.jssymlinkfssymlink-traversal
Intervalia
Intervalia

Reputation: 10965

Is there a way to determine the destination path of a symlink in node?

Situation

I just ran into an odd situation that should not happen often, but I would like to prevent it from ever happening again.

I have a chunk of code that creates a deep dive directory list of all the files in a source folder and all of its children folders.

In general this has never been a problem, until today.

I had a fellow dev that accidentally set a symlink of a sub folder to point back at the parent folder. This caused my deep dive to recuse until it crashed.

For example:

topfolder
topfolder/sub1 - real folder
topfolder/sub2 - symlink back to topfolder

My code read all the files in topfolder and then all files in topfolder/sub1 with no problems. Then, since topfolder/sub2 points back to topfolder I read all the files in topfolder/sub2, which are the same as in topfolder and then topfolder/sub2/sub1 and then topfolder/sub2/sub2 and on to topfolder/sub2/sub2/sub2, etc.

My question

Is there a way, in node.js to determine the destination of a symlink? I figure if I can create a list of folders I have read and, when running into the symlink above, I determine that the destination is really a folder I have already read then I just skip that folder.

Thanks in advance...

Upvotes: 2

Views: 1057

Answers (2)

ccalvert
ccalvert

Reputation: 4476

You have two choices (The Node documentation can be hard to use, so I also supply links to geeksforgeeks.) :

  1. fs.readLink on Node or Geeks
  2. fs.readLinkSync on Node or Geeks

Example with readlink:

fs.readlink(fullPath, (err, linkString) => {
    if (err) {
        console.error(err);
    } else {
        console.log('LINK STRING', linkString);
    }
});

With readlinkSync:

const linkString = fs.readlinkSync(fullPath);
debug('LINK STRING', linkString);

Upvotes: 1

Azami
Azami

Reputation: 2161

Is there a way, in node.js to determine the destination of a symlink?

Yes. fs.readlink(dir) will return the destination of the symlink if it is one, an error otherwise.

fs.readlink("sub2", function(err, destination){
  if(err)
    //sub2 is not a symlink, proceed to go into it
  else if(destination)
    //sub2 is a symlink, check if 'destination' is a folder we have already been through
});

Upvotes: 3

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