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HEASOFT / SAS initialization process: Tips and tricks.

SAS 10.0.0 requires HEASOFT to be initialized by start. In fact, the SAS initialization script checks for the LHEASOFT environment variable to be already defined, aborting if this is not the case.
We recommend you to include the HEASOFT initialization script in your login script. The following is a snippet of code to be included in your account's .bashrc file:
if [ -z "$LHEASOFT" -a -d "/path_to_where_you_have_installed_HEASOFT" ] ; then
export HEADAS=/path_to_where_you_have_installed_HEASOFT
. $HEADAS/headas-init.sh
fi
A similar piece of code could be included in your account's .cshrc if it uses the tcsh shell.
We do not recommend to include the SAS initialization script into the login script. Why?
The SAS initialization script modifies heavily the LD_LIBRARY_PATH (DYLD_LIBRARY_PATH on the Mac OS X operating system) and therefore this could clash with other tools.
We suggest you to dedicate a single terminal to run SAS, initializing the SAS and subsequently running all the SAS commands on such terminal. To run any other software tools, it is better to launch an alternate terminal, without SAS initialization. This is our recommended procedure especially to run "Xspec", despite the fact that this is a tool included with HEASOFT.