Installtion Error For Ns 2.27 On Ubuntu 12.04

following error shown when i tried the command:
cd ns-allinone-2.27/ &&export CC=gcc41 CXX=g++41 && ./install


============================================================
* Testing for Cygwin environment
============================================================
Cygwin not detected, proceeding with regular install.
============================================================
* Build XGraph-12.1
============================================================
loading cache ./config.cache
checking for a BSD compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking whether make sets ${MAKE}... yes
checking for working aclocal... found
checking for working autoconf... found
checking for working automake... found
checking for working autoheader... found
checking for working makeinfo... missing
checking if malloc debugging is wanted... no
checking for gcc... gcc41
checking whether the C compiler (gcc41 ) works... no
configu error: installation or configuration problem: C compiler cannot create executables.
make: *** No targets specified and no makefile found. Stop.
Can not create xgraph; But xgraph is an optional package, continuing...
============================================================
* Build CWeb
============================================================
Making cweb
gcc -g -c -o ctangle.o ctangle.c
ctangle.w:75:12: warning: conflicting types for built-in function ‘strlen’ [enabled by default]
gcc -g -DCWEBINPUTS=\"/usr/local/lib/cweb\" -c common.c
common.w:1409:12: warning: conflicting types for built-in function ‘strlen’ [enabled by default]
common.w: In function ‘fatal’:
common.w:1176:1: warning: format not a string literal and no format arguments [-Wformat-security]
gcc -g -o ctangle ctangle.o common.o
gcc -g -c -o cweave.o cweave.c
cweave.w:79:12: warning: conflicting types for built-in function ‘strlen’ [enabled by default]
cweave.w: In function ‘print_cat’:
cweave.w:1739:1: warning: format not a string literal and no format arguments [-Wformat-security]
gcc -g -o cweave cweave.o common.o
ln: failed to create symbolic link `cweave': File exists
ln: failed to create symbolic link `ctangle': File exists
============================================================
* Build Stanford GraphBase
============================================================
Making sgb
gcc41 -g -I/usr/local/sgb/include -DDATA_DIRECTORY=\"/usr/local/sgb/data/\" -c gb_io.c
make: gcc41: Command not found
make: *** [gb_io.o] Error 127
Unable to create sgb library, but it's optional, so continuing...
============================================================
* Build GT-ITM
============================================================
sgb lib not found. gt-itm & sgb2ns could not be installed. Continuing..
============================================================
* Build zlib
============================================================
Building static library libz.a version 1.1.4 with gcc41.
Checking for unistd.h... No.
Checking for errno.h... No.
Checking for mmap support... No.
gcc41 -O -DNO_ERRNO_H -c -o example.o example.c
make: gcc41: Command not found
make: *** [example.o] Error 127
Zlib make failed, but it's optional Continue ...
============================================================
* Build tcl8.4.5
============================================================
loading cache ./config.cache
checking whether to use symlinks for manpages... no
checking compression for manpages... no
checking for gcc... gcc41
checking whether the C compiler (gcc41 ) works... no
configu error: installation or configuration problem: C compiler cannot create executables.
tcl8.3.2 configuration failed! Exiting ...
Tcl is not part of the ns project. Please see www.Scriptics.com
to see if they have a fix for your platform.



please help