Every stream has a stream position, which advances automatically when you read from or write to the stream. Stream position is represented either as a simple long, or as an fpos_t, defined in <stdio.h>. fpos_t has two advantages over long. First, it can have a greater range than long. Second, it retains multibyte state when operating on wide-oriented streams, so you can record and restore not only position, but that conversion state too. Five functions exist to manipulate the stream position:

#include <stdio.h>
long ftell(FILE *stream);
int fseek(FILE *stream, long offset, int whence);
int fgetpos(FILE *stream, fpos_t *pos);
int fsetpos(FILE *stream, const fpos_t *pos);
void rewind(FILE *stream);

ftell and fgetpos get the current stream position. fseek and fsetpos set the current position. fseek takes an addition argument whence, which has the following meanings:

rewind has two effects. It sets the stream position to the start of the stream, and clears the error and end-of-file indicators.