NS2安装成功后（./install之后）有下面一段信息，要求将一些路径添加到环境变量中：
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Please put /home/chen/Downloads/ns-allinone-2.35/bin:/home/chen/Downloads/ns-allinone-2.35/tcl8.5.10/unix:/home/chen/Downloads/ns-allinone-2.35/tk8.5.10/unix
into your PATH environment; so that you'll be able to run itm/tclsh/wish/xgraph.
IMPORTANT NOTICES:
(1) You MUST put /home/chen/Downloads/ns-allinone-2.35/otcl-1.14, /home/chen/Downloads/ns-allinone-2.35/lib, into
your LD_LIBRARY_PATH environment variable.
If it complains about X libraries, add path to your X libraries into LD_LIBRARY_PATH.
If you are using csh, you can set it like:
setenv LD_LIBRARY_PATH <paths>
If you are using sh, you can set it like:
export LD_LIBRARY_PATH=<paths>
(2) You MUST put /home/chen/Downloads/ns-allinone-2.35/tcl8.5.10/library into your TCL_LIBRARY environmental variable.
Otherwise ns/nam will complain during startup.
After these steps, you can now run the ns validation suite with cd ns-2.35; ./validate
For trouble shooting, please first read ns problems page
http://www.isi.edu/nsnam/ns/ns-problems.html. Also search the ns mailing list archive
for related posts.
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具体添加路径的方法是这样的：
在命令行下进入/etc目录，有一个名为profile的文件，用vi打开，在文件最后添加下面这样一段：
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PATH=/home/chen/Downloads/ns-allinone-2.35/bin:/home/chen/Downloads/ns-allinone-2.35/tcl8.5.10/unix:/home/chen/Downloads/ns-allinone-2.35/tk8.5.10/unix:$PATH;
export PATH
LD_LIBRARY_PATH=/home/chen/Downloads/ns-allinone-2.35/otcl-1.14:/home/chen/Downloads/ns-allinone-2.35/lib:$LD_LIBRARY_PATH;
export LD_LIBRARY_PATH
TCL_LIBRARY=/home/chen/Downloads/ns-allinone-2.35/tcl8.5.10/library:$TCL_LIBRARY
export TCL_LIBRARY
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保存退出，然后再打命令 #source profile，使之立即有效。
输入命令#env 就可以查看到刚才添加的路径了。