Gets the current position of a file pointer, without locking the thread.
These functions are non-locking versions of ftell and _ftelli64, respectively. They are identical to ftell and _ftelli64except that they are not protected from interference by other threads. These functions might be faster because they do not incur the overhead of locking out other threads. Use these functions only in thread-safe contexts such as single-threaded applications or where the calling scope already handles thread isolation.
For more compatibility information, see Compatibility in the Introduction.