How to get Magento 2 base directory programmatically

You can get the Magento 2 base directory the same way as in Magento 1.x: it is stored in the constant BP.

See also other filesystem topics:

• How to get a module filesystem path programmatically
• How to get an absolute media (image) path programmatically by a relative path
• How to write a file programmatically
• How to create or delete a file in the temporary directory