LSEEK(2-SVR4)       RISC/os Reference Manual        LSEEK(2-SVR4)



NAME
     lseek - move read/write file pointer

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

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

DESCRIPTION
     fildes is a file descriptor returned from a creat, open,
     dup, or fcntl 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.  Note that
     if fildes is a remote file descriptor and offset is nega-
     tive, lseek returns the file pointer even if it is negative.

     lseek allows the file pointer to be set beyond the existing
     data in the file. If data are later written at this point,
     subsequent 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.

     lseek fails and the file pointer remains unchanged if one or
     more of the following are true:

     EBADF          fildes is not an open file descriptor.

     ESPIPE         fildes is associated with a pipe or fifo.

     EINVAL         whence is not SEEK_SET, SEEK_CUR, or
                    SEEK_END. The process also gets a SIGSYS sig-
                    nal.

     EINVAL         fildes is not a remote file descriptor, and
                    the resulting file pointer would be negative.

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





                        Printed 11/19/92                   Page 1

LSEEK(2-SVR4)       RISC/os Reference Manual        LSEEK(2-SVR4)



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

DIAGNOSTICS
     Upon successful completion, a non-negative integer indicat-
     ing the file pointer value is returned.  Otherwise, a value
     of -1 is returned and errno is set to indicate the error.
















































 Page 2                 Printed 11/19/92