confusion about expansion

* confusion about expansion
@ 2014-03-12 14:00 Lars Huttar
  2014-03-12 14:05 ` Wolfgang Schuster
  0 siblings, 1 reply; 7+ messages in thread
From: Lars Huttar @ 2014-03-12 14:00 UTC (permalink / raw)
  To: mailing list for ConTeXt users

Hello,
I've got a running page head like this in my document:

\def\CurrentUser{\cldcontext{os.resultof"whoami"}}

\def\Markname { Compiled \date by \CurrentUser  \LUATEX +\ConTeXt\
\contextversion }

and later:

\setlayer[cropmark][preset=lefttop,x=3cm,y=-1.5\lineheight]{\Markname}

But when I run this, I get a UCS error that seems to indicate that the
*result* of \CurrentUser ("waxhaw\huttar") is getting parsed as a
command sequence.

Here's the error:

! Undefined control sequence.

 1 >>  % see ConTeXt wiki http://wiki.contextgarden.net/Imposition#Cut_marks
 2
 3     %% TODO: make sure this doesn't reevaluate every time
 4     %% the command sequence is used!
 5     \define\CurrentUser{\cldcontext{os.resultof"whoami"}}
 6
 7     \def\Markname { Compiled \date by \CurrentUser  \LUATEX
+\ConTeXt\ \conte
xtversion. SVN  }
...

l.1 waxhaw\huttar

\cldcontext #1x-\directlua {context(#1)}

\Markname #- Compiled \date by \CurrentUser
                                            \LUATEX +\ConTeXt \
\contextvers...
l.24 ...t=lefttop,x=3cm,y=-1.5\lineheight]{\Markname
                                                  }

How can I change the definition of \CurrentUser, or \Markname, to output
the result of \CurrentUser as-is, instead of parsing the result?
I tried (somewhat blindly) changing \def to \define, but it didn't make
any difference.

At the same time, I want to make sure that the processor won't be making
an OS system call to "whoami" every time \CurrentUser is evaluated: I
want it to happen only once, when \CurrentUser is defined.

Here is my complete working example:

\def\CurrentUser{\cldcontext{os.resultof"whoami"}}

\def\Markname { Compiled \date by \CurrentUser \LUATEX +\ConTeXt\
\contextversion. }

\setuplayout[location=middle,marking=on]

\definelayer[cropmark][state=repeat,width=\paperwidth,height=\paperheight]

\setupbackgrounds[page][background=cropmark]

\setlayer[cropmark][preset=lefttop,x=3cm,y=-1.5\lineheight]{\Markname}

\starttext

Foo

\stoptext

Thanks for any help.
Lars

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