Compare the execution environment of numerous shells, both sourced and running a script.

compare_shells

#!/bin/sh
# creates env.{source|run}.SHELL, diff them for details for details.
# It is not fancy.
# Usage: compare_shells

for MY_SHELL in zsh rbash bash sh tcsh csh ksh dash; do
  THE_SHELL=`which $MY_SHELL 2>/dev/null`
  if [ -x "$THE_SHELL" ]; then
     echo "$THE_SHELL"
     echo "$THE_SHELL" | grep 'cs' >/dev/null && SRC='source' || SRC='.'

     cat << EOF > runner.tmp
#!$THE_SHELL
$SRC ./subrunner.tmp | sort -u > 'env.source.$MY_SHELL' 
"$THE_SHELL" ./subrunner.tmp | sort -u > 'env.run.$MY_SHELL' 
EOF
     cat << EOF > subrunner.tmp
#!$THE_SHELL
set
env
printenv
EOF
     chmod +x runner.tmp subrunner.tmp
     ./runner.tmp
  fi
done
rm -f runner.tmp subrunner.tmp