llseek man page on SmartOS

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LLSEEK(2)							     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 supplied offset.

       A  "hole" is defined as a contiguous range of bytes in a file, all hav‐
       ing 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. Applica‐
       tions 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	 exis‐
       tence  of  a  hole at the end of every data region allows for easy pro‐
       gramming 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  sys‐
		 tem  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  sup‐
		 plied	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)

				  Apr 1, 2005			     LLSEEK(2)
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