FSEEK(3) Linux Programmer's Manual FSEEK(3)
fgetpos, fseek, fsetpos, ftell, rewind - reposition a stream
int fseek(FILE *stream, long offset, int whence);
long ftell(FILE *stream);
void rewind(FILE *stream);
int fgetpos(FILE *stream, fpos_t *pos);
int fsetpos(FILE *stream, fpos_t *pos);
The fseek function sets the file position indicator for the stream pointed to by stream.
The new position, measured in bytes, is obtained by adding offset bytes to the position
specified by whence. If whence is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is
relative to the start of the file, the current position indicator, or end-of-file, respec-
tively. A successful call to the fseek function clears the end-of-file indicator for the
stream and undoes any effects of the ungetc(3) function on the same stream.
The ftell function obtains the current value of the file position indicator for the stream
pointed to by stream.
The rewind function sets the file position indicator for the stream pointed to by stream
to the beginning of the file. It is equivalent to:
(void)fseek(stream, 0L, SEEK_SET)
except that the error indicator for the stream is also cleared (see clearerr(3)).
The fgetpos and fsetpos functions are alternate interfaces equivalent to ftell and fseek
(with whence set to SEEK_SET), setting and storing the current value of the file offset
into or from the object referenced by pos. On some non-UNIX systems an fpos_t object may
be a complex object and these routines may be the only way to portably reposition a text
The rewind function returns no value. Upon successful completion, fgetpos, fseek, fsetpos
return 0, and ftell returns the current offset. Otherwise, -1 is returned and the global
variable errno is set to indicate the error.
EBADF The stream specified is not a seekable stream.
EINVAL The whence argument to fseek was not SEEK_SET, SEEK_END, or SEEK_CUR.
The function fgetpos, fseek, fsetpos, and ftell may also fail and set errno for any of the
errors specified for the routines fflush(3), fstat(2), lseek(2), and malloc(3).
The fgetpos, fsetpos, fseek, ftell, and rewind functions conform to ANSI X3.159-1989
BSD MANPAGE 1993-11-29 FSEEK(3)