Originální popis anglicky:
fseek, fseeko - reposition a file-position indicator in a stream
Návod, kniha: POSIX Programmer's Manual
#include <stdio.h>
int fseek(FILE *
stream, long
offset, int
whence);
int fseeko(FILE *stream, off_t offset,
int whence);
The
fseek() function shall set the file-position indicator for the stream
pointed to by
stream. If a read or write error occurs, the error
indicator for the stream shall be set and
fseek() fails.
The new position, measured in bytes from the beginning of the file, shall be
obtained by adding
offset to the position specified by
whence.
The specified point is the beginning of the file for SEEK_SET, the current
value of the file-position indicator for SEEK_CUR, or end-of-file for
SEEK_END.
If the stream is to be used with wide-character input/output functions, the
application shall ensure that
offset is either 0 or a value returned by
an earlier call to
ftell() on the same stream and
whence is
SEEK_SET.
A successful call to
fseek() shall clear the end-of-file indicator for
the stream and undo any effects of
ungetc() and
ungetwc() on the
same stream. After an
fseek() call, the next operation on an update
stream may be either input or output.
If the most recent operation, other than
ftell(), on a given stream is
fflush(), the file offset in the underlying open file description shall
be adjusted to reflect the location specified by
fseek().
The
fseek() function shall allow the file-position indicator to be set
beyond the end of existing data in the file. If data is later written at this
point, subsequent reads of data in the gap shall return bytes with the value 0
until data is actually written into the gap.
The behavior of
fseek() on devices which are incapable of seeking is
implementation-defined. The value of the file offset associated with such a
device is undefined.
If the stream is writable and buffered data had not been written to the
underlying file,
fseek() shall cause the unwritten data to be written
to the file and shall mark the
st_ctime and
st_mtime fields of
the file for update.
In a locale with state-dependent encoding, whether
fseek() restores the
stream's shift state is implementation-defined.
The
fseeko() function shall be equivalent to the
fseek() function
except that the
offset argument is of type
off_t.
The
fseek() and
fseeko() functions shall return 0 if they
succeed.
Otherwise, they shall return -1 and set
errno to indicate the error.
The
fseek() and
fseeko() functions shall fail if,
either the
stream is unbuffered or the
stream's buffer
needed to be flushed, and the call to
fseek() or
fseeko() causes
an underlying
lseek() or
write() to be invoked, and:
- EAGAIN
- The O_NONBLOCK flag is set for the file descriptor and the
process would be delayed in the write operation.
- EBADF
- The file descriptor underlying the stream file is not open
for writing or the stream's buffer needed to be flushed and the file is
not open.
- EFBIG
- An attempt was made to write a file that exceeds the
maximum file size.
- EFBIG
- An attempt was made to write a file that exceeds the
process' file size limit.
- EFBIG
- The file is a regular file and an attempt was made to write
at or beyond the offset maximum associated with the corresponding
stream.
- EINTR
- The write operation was terminated due to the receipt of a
signal, and no data was transferred.
- EINVAL
- The whence argument is invalid. The resulting
file-position indicator would be set to a negative value.
- EIO
- A physical I/O error has occurred, or the process is a
member of a background process group attempting to perform a
write() to its controlling terminal, TOSTOP is set, the process is
neither ignoring nor blocking SIGTTOU, and the process group of the
process is orphaned. This error may also be returned under
implementation-defined conditions.
- ENOSPC
- There was no free space remaining on the device containing
the file.
- ENXIO
- A request was made of a nonexistent device, or the request
was outside the capabilities of the device.
- EOVERFLOW
- For fseek(), the resulting file offset would be a
value which cannot be represented correctly in an object of type
long.
- EOVERFLOW
- For fseeko(), the resulting file offset would be a
value which cannot be represented correctly in an object of type
off_t.
- EPIPE
- An attempt was made to write to a pipe or FIFO that is not
open for reading by any process; a SIGPIPE signal shall also be sent to
the thread.
- ESPIPE
- The file descriptor underlying stream is associated
with a pipe or FIFO.
The following sections are informative.
None.
None.
None.
None.
fopen() ,
fsetpos() ,
ftell() ,
getrlimit() ,
lseek() ,
rewind() ,
ulimit() ,
ungetc() ,
write() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<stdio.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
