Unix/Linux Go Back    


OpenSolaris 2009.06 - man page for llseek (opensolaris section 2)

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


llseek(2)				   System Calls 				llseek(2)

NAME
       llseek - move extended read/write file pointer

SYNOPSIS
       #include <sys/types.h>
       #include <unistd.h>

       offset_t llseek(int fildes, offset_t offset, int whence);

DESCRIPTION
       The  llseek() function sets the 64-bit extended file pointer associated with the open file
       descriptor specified by fildes as follows:

	   o	  If whence is SEEK_SET, the pointer is set to offset bytes.

	   o	  If whence is SEEK_CUR, the pointer is set to its current location plus offset.

	   o	  If whence is SEEK_END, the pointer is set to the size of the file plus offset.

	   o	  If whence is SEEK_HOLE, the offset of the start of the next hole  greater  than
		  or  equal  to the supplied offset is returned. The definition of a hole immedi-
		  ately follows this list.

	   o	  If whence is SEEK_DATA, the file pointer is set to the start of the  next  non-
		  hole file region greater than or equal to the supplied offset.

       A  "hole"  is  defined  as  a contiguous range of bytes in a file, all having the value of
       zero, but not all zeros in a file are guaranteed to be represented as holes returned  with
       SEEK_HOLE.  Filesystems	are  allowed  to  expose  ranges of zeros with SEEK_HOLE, but not
       required to. Applications can use SEEK_HOLE to  optimise  their	behavior  for  ranges  of
       zeros,  but  must  not  depend on it to find all such ranges in a file. The existence of a
       hole at the end of every data region allows for easy programming and implies that  a  vir-
       tual hole exists at the end of the file.

       For  filesystems  that do not supply information about holes, the file will be represented
       as one entire data region.

       Although each file has a 64-bit file pointer associated with it, some existing file system
       types  (such as tmpfs) do not support the full range of 64-bit offsets.	In particular, on
       such file systems, non-device files remain limited to offsets of less than two  gigabytes.
       Device drivers may support offsets of up to 1024 gigabytes for device special files.

       Some  devices are incapable of seeking. The value of the file pointer associated with such
       a device is undefined.

RETURN VALUES
       Upon successful completion, llseek() returns the resulting pointer location as measured in
       bytes from the beginning of the file. Remote file descriptors are the only ones that allow
       negative file pointers. Otherwise, -1 is returned, the file pointer remains unchanged, and
       errno is set to indicate the error.

ERRORS
       The llseek() function will fail if:

       EBADF	 The fildes argument is not an open file descriptor.

       EINVAL	 The  whence argument is not SEEK_SET, SEEK_CUR, or SEEK_END; the offset argument
		 is not a valid offset for this file system type; or the fildes argument is not a
		 remote file descriptor and the resulting file pointer would be negative.

       ENXIO	 For  SEEK_DATA,  there  are  no  more data regions past the supplied offset. For
		 SEEK_HOLE, there are no more holes past the supplied offset.

       ESPIPE	 The fildes argument is associated with a pipe or FIFO.

SEE ALSO
       creat(2), dup(2), fcntl(2), lseek(2), open(2)

SunOS 5.11				    1 Apr 2005					llseek(2)
Unix & Linux Commands & Man Pages : ©2000 - 2018 Unix and Linux Forums


All times are GMT -4. The time now is 07:10 PM.