[ncl-install] cannot find -lX11

[wyzhj0920]

hi,I have installed ncl5.1.1. My operation system is ubuntu 8.1. The version of nclis ncl_ncarg-5.1.1.Linux_i686_gcc432.tar.gz. The infomations of my compier are:

  1. Intel(R) Fortran Compiler 10.1 for Linux*
  2. Intel(R) C++ Compiler 10.1 for Linux*
  3. GNU Fortran (Ubuntu 4.3.2-1ubuntu12) 4.3.2
I refer to the doucument of http://www.ncl.ucar.edu/Download/install.shtml. After I installed the ncl, these commands is normal.
  1.  ng4ex gsun01n
  2.  ncl gsun01n.ncl
but I executing this command (ncargex cpex08) gives the below error.
=====================================================================
Compiling and linking...
gfortran -fPIC -fno-second-underscore -fno-range-check -o cpex08 cpexcc.f cpex08.f -L/usr/local/ncarg/lib -lncarg -lncarg_gks -lncarg_c -lX11 -lXext -lpng -lz
/usr/bin/ld: cannot find -lX11
collect2: ld returned 1 exit status

The compile and link failed.
======================================================================
So what's the problem? and what should I do??
Many thanks....
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