FSEEK(3) BSD Programmer's Manual FSEEK(3)NAME
fgetpos, fseek, fseeko, fsetpos, ftell, ftello, rewind - reposition a
stream
SYNOPSIS
#include <stdio.h>
int
fgetpos(FILE *stream, fpos_t *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);
DESCRIPTION
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, respective-
ly. A successful call to the fseek() function clears the end-of-file in-
dicator 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 indi-
cator 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
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 stream.
RETURN VALUES
The rewind() function returns no value. Upon successful completion, fget-
pos(), fseek(), fseeko(), fsetpos() return 0 and ftell() and ftello() re-
turn 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.
ERRORS
[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 functions fgetpos(), fseek(), fseeko(), fsetpos(), ftell(), and ftel-
lo() may also fail and set errno for any of the errors specified for the
routines fflush(3), fstat(2), lseek(2), and malloc(3).
SEE ALSOlseek(2)STANDARDS
The fgetpos(), fsetpos(), fseek(), ftell(), and rewind() functions con-
form 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").
MirOS BSD #10-current February 21, 2000 1