\ExecuteOptions{shell}
\newif\ifcmd
\newif\ifnix
\ProcessOptions\relax
%% test if shell escape really works
\ifShellEscape
	\def\tmpfile{w18-test-\the\year\the\month\the\day\the\time.tex}
	\immediate\write18{echo t > "\tmpfile"}
	\IfFileExists{\tmpfile}{\ifcmdtrue}{\ifcmdfalse}
		\ifcmpd
		\else
			\immediate\write18{touch \tmpfile}
			\IfFileExists{\tmpfile}{\ifnixtrue}{\ifnixfalse}
		\fi
	\ifcmd
		\IfFileExists{\tmpfile}{\ShellEscapetrue}{\ShellEscapefalse}
		\immediate\write18{del "\tmpfile"}
	\else
		\ifnix
			\IfFileExists{\tmpfile}{\ShellEscapetrue}{\ShellEscapefalse}
			\immediate\write18{rm -f \tmpfile}
			\immediate\write18{rm -f "\jobname.gnuploterrors"}
		\fi
	\fi
\fi