Shell command as a variable in Makefile

Question

I have the following (very simplified) Makefile:

# Makefile MAKESH=shell USER=$($MAKESH logname)

which aims to store my login name in the USER variable as if the $(shell logname) command was invoked. However this doesn't happen. I suspect that it's due to the way make evaluates variables.

Does anyone have some more insight to this or a possible workaround i.e. explicitly tell make that $MAKESH is actually the shell command?

Thanks.

Edit

Consider the following example:

#parent.mk ... include child.mk ... ------------------- #child.mk export $(shell logname)/path1 export $(shell logname)/path2 ------------------- #bash_script.sh ... source child.mk ...

(in this example, sourcing child.mk fails)

Essentially, what I wanted to do is to create a file that exports pathnames depending on the current user. The syntax should be valid both for makefiles and bash scripts, since it can be included/sourced from both places.

I also wanted to do subtle changes to these files, since they are part of a larger project and the interconnections are a bit confusing.

I have finally decided to go with this:

#parent.mk ... export logname=$(shell logname) include child.mk ... ------------------- #child.mk export $(logname)/path1 export $(logname)/path2 ------------------- #bash_script.sh ... source child.mk ...

which is quite hacky, a tiny bit dangerous, but works. If you know a more elegant way/aprroach, let me know.

Finally, thank you for your solutions (and your warnings), which are valid for the pre-editted question.

Why would you want this? BTW it is not the shell command, but the shell function. — reinierpost
– reinierpost, Commented Jan 28, 2013 at 16:48
the variable USER will not be evaluated until it is used. If you want to get it evaluated immediately use the form := for the assignment — Anya Shenanigans
– Anya Shenanigans, Commented Jan 28, 2013 at 17:04

William · Accepted Answer · 2013-01-28 16:51:51Z

The syntax should be

USER = $(shell logname)

I don't know why you want to put "shell" in a variable and screw up the function syntax, but if you really insist, try this:

$(eval USER=$$($MAKESH logname))

The $(eval ...) function will just turn it into the first form above, though, so it's wasted effort. (Unless your really trying to do something trickier than your example suggests.)

reinierpost · Accepted Answer · 2013-01-28 17:01:34Z

2

MAKESH=shell $(eval USER=$$($(MAKESH) logname)) $(info USER is $(USER))

Avoid if possible.

answered Jan 28, 2013 at 17:01

reinierpost

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1 Comment

Brain-free Over a year ago

Both answers are the same, but this one also includes the very useful $(info) function.

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