fgetpos, fseek, fseeko, fsetpos, ftell, ftello, rewind -- reposition a
Standard C Library (libc, -lc)
fseek(FILE *stream, long offset, int whence);
fgetpos(FILE * restrict stream, fpos_t * restrict pos);
fsetpos(FILE *stream, const fpos_t *pos);
fseeko(FILE *stream, off_t offset, int whence);
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 endof-file
indicator for the stream and undoes any effects of the ungetc(3)
and ungetwc(3) functions 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
Since rewind() does not return a value, an application wishing to detect
errors should clear errno, then call rewind(), and if errno is non-zero,
assume an error has occurred.
The fseeko() function is identical to fseek(), except it takes an off_t
argument instead of a long. Likewise, the ftello() function is identical
to ftell(), except it returns an off_t.
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
If the stream is a wide character stream (see fwide(3)), the position
specified by the combination of offset and whence must contain the first
byte of a multibyte sequence.
The rewind() function returns no value.
The fgetpos(), fseek(), fseeko(), and fsetpos() functions return the
value 0 if successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
Upon successful completion, ftell() and ftello() return the current offset.
Otherwise, -1 is returned and the global variable errno is set to
indicate the error.
[EBADF] The stream argument is not a seekable stream.
[EINVAL] The whence argument is invalid or the resulting fileposition
indicator would be set to a negative value.
[EOVERFLOW] The resulting file offset would be a value which cannot
be represented correctly in an object of type
off_t for fseeko() and ftello() or long for fseek()
[ESPIPE] The file descriptor underlying stream is associated
with a pipe or FIFO or file-position indicator value
is unspecified (see ungetc(3)).
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).
lseek(2), clearerr(3), fwide(3), ungetc(3), ungetwc(3)
The fgetpos(), fsetpos(), fseek(), ftell(), and rewind() functions conform
to ISO/IEC 9899:1990 (``ISO C89'').
The fseeko() and ftello() functions conform to IEEE Std 1003.1-2001
FreeBSD 5.2.1 October 12, 2002 FreeBSD 5.2.1 [ Back ]