nasty env vars

[Mark L. <la...@mi...>]

We have one piece of software that requires a nasty env var to be set. The
environment variable contains double-quotes and curly braces, for example:

BEGIN{require"/foo/init.pl"}

(perl hackers will recognize that as perl syntax. Don't ask me who decided to
store a perl one-liner in an env var!)

In csh, you can set it with

 setenv FOO 'BEGIN{require"/foo/init.pl"}'

However, you will be hardpressed to get this to work in a module! Try it! The
double quotes and the curly braces will ruin your day, so if you tried that
line "as is" in your modulefile, you will get

 BEGINrequire/foo/init.pl

as the env var! This is because of several levels of evals and backticks that
process the line. The curly braces are csh syntax for filename substitution, so
they get erased. The quotes get erased too. The other problem is that you can't
nest quotes like ' or ", and you can't escape " inside a string, only outside a
string (unlike C syntax). You can turn off the {} mangling by using 'set
noglob' in csh, but you have to 'set noglob' on a different line than the one
your are parsing, and eval only accepts one liners! eg

#this works
 eval set noglob
 eval setenv FOO BEGIN{require\"/foo/init.pl\"}

# this doesn't
 eval "set noglob; setenv FOO BEGIN{require\"/foo/init.pl\"}"


ARGH!

I've tried all manner of quoting levels, only to really tear my hair out.  At
some point I got to

 setenv FOO {'"BEGIN{require"\\\"/foo/init.pl\\\""}"'}

which almost worked, but it doesn't. Also, anything that I could kinda make
work would break all the other shell syntaxes.

Any Ideas?


-Mark



Mark Lakata, Staff Engineer    1225 Charleston Road       voice 650-567-5170
MIPS Technologies              Mountain View CA 94043     fax   650-567-5002