lseek(2)                                                    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
             lseek moves a read/write file pointer.  fildes is a file
             descriptor returned from a creat, open, dup, fcntl, pipe, or
             ioctl system call.  lseek sets the file pointer associated
             with fildes as follows:

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

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

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

             On success, lseek returns the resulting pointer location, as
             measured in bytes from the beginning of the file.

             lseek allows the file pointer to be set beyond the existing
             data in the file.  If data is later written at this point,
             subsequent reads in the gap between the previous end of data
             and the newly written data return bytes of value 0 until data
             is written into the gap.

          Return Values
             On success, lseek returns a non-negative integer indicating
             the file pointer value.  On failure, lseek returns -1, sets
             errno to identify the error, and the file pointer remains
             unchanged.

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

          Errors
             In the following conditions, lseek fails and sets errno to:





                           Copyright 1994 Novell, Inc.               Page 1

      lseek(2)                                                    lseek(2)


            EBADF          fildes is not an open file descriptor.

            ESPIPE         fildes is associated with a pipe or fifo.

            EINVAL         The resulting file pointer would be negative.

                           fildes is a remote file descriptor accessed
                           using NFS, the Network File System, and the
                           resulting file pointer would be negative.

            ENOSYS         The device for fstype does not support lseek.

      REFERENCES
            creat(2), dup(2), fcntl(2), open(2)

      NOTICES
         Considerations for Threads Programming
            Open file descriptors are a process resource and available to
            any sibling thread; if used concurrently, actions by one
            thread can interfere with those of a sibling.  For example,
            the position of the file pointer is maintained per file
            descriptor, not per thread.

            The pread(2) and pwrite(2) system calls combine positioning
            and I/O in a single operation.























                          Copyright 1994 Novell, Inc.               Page 2