Description

   The lseek function can position a fixed-length record-access
   file with no carriage control or a stream-access file on any
   byte offset, but can position all other files only on record
   boundaries.

   The available Standard I/O functions position a record file at
   its first byte, at the end-of-file, or on a record boundary.
   Therefore, the arguments given to lseek must specify either
   the beginning or end of the file, a 0 offset from the current
   position (an arbitrary record boundary), or the position returned
   by a previous, valid lseek call.

   This function returns the new file position as an integer of type
   off_t which, like the offset argument, is either a 64-bit integer
   if _LARGEFILE is defined, or a 32-bit integer if not.

   For a portable way to position an arbitrary byte location with
   any type of file, see the fgetpos and fsetpos functions.

                                CAUTION

      If, while accessing a stream file, you seek beyond the
      end-of-file and then write to the file, the lseek function
      creates a hole by filling the skipped bytes with zeros.

      In general, for record files, lseek should only be directed
      to an absolute position that was returned by a previous
      valid call to lseek or to the beginning or end of a file.
      If a call to lseek does not satisfy these conditions, the
      results are unpredictable.

   See also open, creat, dup, dup2, and fseek.