From 6a49d0127656c685f2769333cbb7f9d034947501 Mon Sep 17 00:00:00 2001
From: Dominik Smith <smith@th.physik.uni-frankfurt.de>
Date: Wed, 27 Jul 2022 16:30:44 +0200
Subject: [PATCH] Updated README.md to include instructions regarding the -p
 and -a options of config.sh and config.csh.

---
 README.md | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 160e667499..8cc43e6a7b 100644
--- a/README.md
+++ b/README.md
@@ -138,11 +138,18 @@ From your build directory, then call
 After your build is complete, before running any part of CbmRoot from a shell,
 a large number of environment variables must be set, which contain various
 library and include paths. This is done automatically by executing the "config.sh"
-or "config.csh" script from your CbmRoot build directory. If you are using
-a Bash shell, you can  add the following line to .bashrc to further automate
-this step:
+or "config.csh" script from your CbmRoot build directory. 
 
-    source ~/build_cbmroot/config.sh > /dev/null 2>&1
+Please note, that you must supply the argument "-p" (prepend) or "-a" (append) to 
+these scripts, depending on whether you wish to add the new entries at the front or 
+back of existing environment variables. Failing to do so will cause the variables
+to be overwritten, and may render your shell inoperable. This behavior may be desired
+in some cases, e.g. on the Virgo cluster.
+
+If you are using a Bash shell, you can add the following line to .bashrc to further 
+automate this step:
+
+    source ~/build_cbmroot/config.sh -a > /dev/null 2>&1
 
 The problem with this automatisation is that it frequently results in
 problems if you use more than one combination of FairSoft/FairRoot/Cbmroot.
-- 
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