Bashscripts.org

OK, bash newbie but seasoned programmer/developer. I'm trying to script a bash script to run m4 on a series of files, and I want to pass a bunch of macro definitions to m4 from a bash variable. Something like this:

PRODUCT=Product Name
...
M4MACROS="-D '_PRODUCT_=$PRODUCT' -D '_VERS_=$VERS' -D '_BETA_=$BETA'"
...
m4 ${M4MACROS} (more stuff)

As written above, this doesnt work. M4MACROS is expanded ok (as expected with the double quotes), but when ${M4MACROS} is expanded I hit a problem. Bash, of course, parses out the expansion splitting at spaces even though the individual macro names are in single quotes, which breaks up the macro definitions for m4 and messes everything up. I've looked at eval and other tricks but i'm scratching my head trying to think of a workaround here.

tia,
Tim

have you tried escaping double quotes?



I don't see why this shouldn't work, as always done that for me in that past

Best regards
Fredrik Eriksson

Yeah I tried that .. it didnt work. So far as I can see there is no way do do this because BASH parses out the contents of variable expansion using $IFS separatores but IGNORES quoting. So you cannot use "late" quoting within a variable when the variable may contain (say) filenames with spaces in them.

I would find this extraordinary, but, to be frank, most of the bash syntax strikes me as arcane. And yes I'm aware it's inherited from sh etc, but that doesnt make it less arcane

--Tim