Files

The sticky bit on a Linux directory adds an ownership restriction to removing or renaming entries. It is commonly combined with broad directory write and search permissions so several users can create temporary files without freely removing one another’s entries. The directory permission check and the sticky ownership check both matter; sticky is an additional condition, not a replacement for normal access control. ...

A file descriptor is a small integer used within one process to refer to an open resource. The process’s descriptor table maps that number to an open file description maintained by the kernel. For a regular file, the description includes the current offset and file status flags. Another process can use the same integer for a completely different resource, so the number alone is not a global file identity. ...