Deleted a large file but seeing no increase in free space or decrease of disk usage? Using UNIX or other POSIX OS?
The unlink() is not about removing file, it's about removing a file name. The manpage says: ``unlink - delete a name and possibly the file it refers to''.
Most of the time a file has just one name -- removing it will also remove (free, deallocate) the `body' of file (with one caveat, see below). That's the simple, usual case.
However, it's perfectly fine for a file to have several names (see the link() function), in the same or different directories. All the names will refer to the file body and `keep it alive', so to say. Only when all the names are removed, the body of file actually is freed.
A file's body may *also* be `kept alive' (still using diskspace) by a process holding the file open. The body will not be deallocated (will not free disk space) as long as the process holds it open. In fact, there's a fancy way of resurrecting a file removed by a mistake but still held open by a process...