FSEEK(3) | Library Functions Manual | FSEEK(3) |
fgetpos
, fseek
,
fseeko
, fsetpos
,
ftell
, ftello
,
rewind
— reposition a
stream
Standard C Library (libc, -lc)
#include
<stdio.h>
int
fgetpos
(FILE *restrict stream,
fpos_t *restrict pos);
int
fseek
(FILE *stream,
long offset, int whence);
int
fseeko
(FILE *stream,
off_t offset, int whence);
int
fsetpos
(FILE *stream,
const fpos_t *pos);
long
ftell
(FILE *stream);
off_t
ftello
(FILE *stream);
void
rewind
(FILE *stream);
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) 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 clearerr(3)).
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 for retrieving and setting the current
position in the file, similar to ftell
() and
fseek
(), except that the current position is stored
in an opaque object of type fpos_t pointed to by
pos. These functions provide a portable way to seek to
offsets larger than those that can be represented by a long
int. They may also store additional state information in the
fpos_t object to facilitate seeking within files
containing multibyte characters with state-dependent encodings. Although
fpos_t has traditionally been an integral type,
applications cannot assume that it is; in particular, they must not perform
arithmetic on objects of this type.
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
]EINVAL
]EOVERFLOW
]fseeko
() and ftello
() or
long for fseek
() and
ftell
().ESPIPE
]The functions fgetpos
(),
fseek
(), fseeko
(),
fsetpos
(), ftell
(),
ftello
(), and rewind
() may
also fail and set errno for any of the errors
specified for the routines fflush(3),
fstat(2),
lseek(2), and
malloc(3).
#include <stdio.h>
#include <sys/types.h>
int
fseeko
(FILE
*stream, off_t offset, int
whence);;
The include file
<sys/types.h>
supplies the
definition for off_t.
lseek(2), clearerr(3), fwide(3), ungetc(3), ungetwc(3), compat(5)
The fgetpos
(),
fsetpos
(), fseek
(),
ftell
(), and rewind
()
functions conform to ISO/IEC 9899:1990
(“ISO C90”).
The fseeko
() and
ftello
() functions conform to IEEE
Std 1003.1-2001 (“POSIX.1”).
March 19, 2004 | macOS 14.6 |