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fseek(3C)		 Standard C Library Functions		     fseek(3C)

NAME
       fseek, fseeko - reposition a file-position indicator in a stream

SYNOPSIS
       #include	<stdio.h>

       int fseek(FILE *stream, long offset, int	whence);

       int fseeko(FILE *stream,	off_t offset, int whence);

DESCRIPTION
       The  fseek()  function  sets the	file-position indicator	for the	stream
       pointed to by stream. The fseeko() function is identical	to fseek() ex-
       cept for	the type of offset.

       The  new	position, measured in bytes from the beginning of the file, is
       obtained	by adding offset to the	position specified  by	whence,	 whose
       values are defined in <stdio.h> as follows:

       SEEK_SET	       Set position equal to offset bytes.

       SEEK_CUR	       Set position to current location	plus offset.

       SEEK_END	       Set position to EOF plus	offset.

       If the stream is	to be used with	wide character input/output functions,
       offset must either be 0 or a value  returned  by	 an  earlier  call  to
       ftell(3C) on the	same stream and	whence must be SEEK_SET.

       A  successful  call to fseek() clears the end-of-file indicator for the
       stream and undoes any effects of	ungetc(3C) and ungetwc(3C) 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(3C), on a	 given	stream
       is  fflush(3C), the file	offset in the underlying open file description
       will be adjusted	to reflect the location	specified by fseek().

       The fseek() function allows the file-position indicator to be  set  be-
       yond  the end of	existing data in the file. If data is later written at
       this point, subsequent reads of data in the gap will return bytes  with
       the value 0 until data is actually written into the gap.

       The  value  of the file offset returned by fseek() on devices which are
       incapable of seeking is undefined.

       If the stream is	writable and buffered data had not been	written	to the
       underlying file,	fseek()	will cause the unwritten data to be written to
       the file	and mark the st_ctime and st_mtime fields of the file for  up-
       date.

RETURN VALUES
       The fseek() and fseeko()	functions return 0 on success; otherwise, they
       returned	-1 and set errno to indicate the error.

ERRORS
       The fseek() and fseeko()	functions will 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(2) or write(2) to	be in-
       voked:

       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 or the process's file	size limit, or
		       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-po-
		       sition 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 per-
		       form a write(2) operation to its	controlling  terminal,
		       TOSTOP  is  set,	 the  process  is neither ignoring nor
		       blocking	SIGTTOU, and the process group of the  process
		       is orphaned.

       ENOSPC	       There  was  no  free space remaining on the device con-
		       taining the file.

       ENXIO	       A request was made of a non-existent device, or the re-
		       quest was outside the capabilities of the device.

       EPIPE	       The  file  descriptor  underlying  stream is associated
		       with a pipe or FIFO.

       EPIPE	       An attempt was made to write to a pipe or FIFO that  is
		       not  open  for reading by any process. A	SIGPIPE	signal
		       will also be sent to the	calling	thread.

       The fseek() function will fail if:

       EOVERFLOW       The resulting file offset would be a value which	cannot
		       be represented correctly	in an object of	type long.

       The fseeko() function will fail if:

       EOVERFLOW       The resulting file offset would be a value which	cannot
		       be represented correctly	in an object of	type off_t.

USAGE
       Although	on the UNIX system an offset returned by ftell()  or  ftello()
       (see  ftell(3C))	is measured in bytes, and it is	permissible to seek to
       positions relative to that offset, portability to non-UNIX systems  re-
       quires  that an offset be used by fseek() directly.  Arithmetic may not
       meaningfully be performed on such an offset, which is  not  necessarily
       measured	in bytes.

       The fseeko() function has a transitional	interface for 64-bit file off-
       sets.  See lf64(5).

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       getrlimit(2),   ulimit(2),    fopen(3UCB),    ftell(3C),	   rewind(3C),
       ungetc(3C), ungetwc(3C),	attributes(5), lf64(5),	standards(5)

SunOS 5.10			  1 Nov	2003			     fseek(3C)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | USAGE | ATTRIBUTES | SEE ALSO

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