http://kor.i2p/books/The%20C%20Programming%20Language%20by%20K&R/chapter8.html
The
system call lseek provides a way to move around in a file without
reading or writing any data: long lseek(int fd, long offset, int origin); sets the current position in the file whose descriptor is fd to offset , which is taken relative to the location specified by origin .
Subsequent reading or writing will begin at that position. origin can
be 0, 1, or 2 to specify that offset is to be measured from the
beginning, from the current position, or from the end of the...