In very rare cases you might need very some very fine-tuned file reading operations in which after reading some part of a file you might need to re-read that part, or you might need to jump over large sections of a file. The two tools for this are tell and seek.

tell can, well, tell you the current position of the filehandle. How far are the reader head from the beginning of the file.

seek can move the current position of the filehandle very fast.