llseek(2) [opensolaris man page]

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 immediately 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  sup-
		  plied 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 virtual 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)

Check Out this Related Man Page

lseek(2)							   System Calls 							  lseek(2)

NAME

       lseek - move read/write file pointer

SYNOPSIS

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

       off_t lseek(int fildes, off_t offset, int whence);

DESCRIPTION

       The lseek() function sets the 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.

       The symbolic constants SEEK_SET, SEEK_CUR, and SEEK_END are defined in the header <unistd.h>.

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

       The  lseek() function allows the file pointer to be set beyond the existing data in the file. If data are later written at this point, sub-
       sequent reads in the gap between the previous end of data and the newly written data will return bytes of value 0 until	data  are  written
       into the gap.

       If  fildes  is a remote file descriptor and offset is negative, lseek() returns the file pointer  even if it is negative. The lseek() func-
       tion will not, by itself, extend the size of a file.

       If fildes refers to a shared memory object, lseek() behaves as if fildes referred to a regular file.

RETURN VALUES

       Upon successful completion, the resulting offset, as measured in bytes from the beginning of the file, is returned. Otherwise, (off_t)-1 is
       returned, the file offset remains unchanged, and errno is set to indicate the error.

ERRORS

       The lseek() 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; or the fildes argument is not a remote file descriptor and the
		       resulting file pointer would be negative.

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

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

USAGE

       The lseek() function has a transitional interface for 64-bit file offsets.  See lf64(5).

       In  multithreaded  applications,  using lseek() in conjunction with a read(2) or write(2) call on a file descriptor shared by more than one
       thread is not an atomic operation.  To ensure atomicity, use pread() or pwrite().

ATTRIBUTES

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

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

SEE ALSO

       creat(2), dup(2), fcntl(2), open(2), read(2), write(2), attributes(5), lf64(5), standards(5)

SunOS 5.10							    17 Apr 2002 							  lseek(2)

Linux and UNIX Man Pages

llseek(2) [opensolaris man page]

Check Out this Related Man Page