FSEEK(3) OpenBSD Programmer's Manual FSEEK(3)NAME
fgetpos, fseek, fseeko, fsetpos, ftell, ftello, rewind - reposition a
fgetpos(FILE *stream, fpos_t *pos);
fseek(FILE *stream, long offset, int whence);
fseeko(FILE *stream, off_t offset, int whence);
fsetpos(FILE *stream, const 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,
respectively. 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 fseeko() function is identical to fseek() except that it takes an
off_t as its offset.
The ftell() function obtains the current value of the file position
indicator for the stream pointed to by stream.
The ftello() function is identical to ftell() except that its return
value is of type off_t.
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
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
The rewind() function returns no value. Upon successful completion,
fgetpos(), fseek(), fseeko(), fsetpos() return 0 and ftell() and ftello()
return the current offset. Otherwise, fseek() and fseeko() return -1 and
the others return a non-zero value 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,
The functions fgetpos(), fseek(), fseeko(), fsetpos(), ftell(), and
ftello() 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 (``ANSI C'') and X/Open Portability Guide
Issue 4 (``XPG4'').
The fseeko() and ftello() functions conform to X/Open Portability Guide
Issue 4 (``XPG4'').
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9