How to fix this warning: file_get_contents(): Unable to find the wrapper "public"?

I need to read some meta information from the downloaded file. But I do not know how to do it.

Here is my code:

// Path form field_file
$file = 'public://directory/filename.txt';
fil开发者_运维技巧e_get_contents($file);

This code causes this warning:

Warning: file_get_contents(): Unable to find the wrapper "public" - did you forget to enable it when you configured PHP?

Any idea of what I am doing wrong, please?

There are three internal stream wrappers private, public and temporary, they are defined in this file.

You may want file_get_mimetype(), file_get_contents is a PHP function and won't be aware of the drupal file api.

file_get_contents(drupal_realpath($file));

Would do the trick for reading.

For an upload take a look at file_save_upload()

I believe that these wrappers aren't available in hook_boot() or some other early stages. So please move your code into another place and check if this would fix the problem.

The fix I'm using is the following code:

echo base_path().variable_get('file_public_path',conf_path().'/files');

It still doesn't explain why streams aren't working.