"Unterminated quoted string" when using variables with quotes in makefile

Question

I have the following makefile:

help:
    @echo "MYVAR = $(MYVAR)"

Which if called works:

» MYVAR="hello" make -f makefile
MYVAR = xxx

But:

» MYVAR='"' make -f makefile 
/bin/sh: 1: Syntax error: Unterminated quoted string
makefile:2: recipe for target 'help' failed
make: *** [help] Error 2

How can I avoid that? Sometimes my variables have simply quotes inside (I deal with json very often)

Answer 1

You have to escape quotation marks.

If you want to store '"' in a variable you have to assign '\"' to it.

And if you want to store " in a variable you have to assign \" to it.

Answer 2

If you want a completely generic quoting mechanism then you have to do this:

First, in your recipe you need to use single quotes around the content where the make variable is to be expanded. This is OK, because make doesn't care about quotes at all, and you need this because it means the only special character you have to worry about is a single quote.

Second, you have to translate all the single quotes in the string into the form '\'', which closes the current single quoted string, adds an escaped single quote, and starts a new single quoted string.

So, something like this:

quotestr = $(subst ','\'',$1)

help:
        @echo 'MYVAR = $(call quotestr,$(MYVAR))'

No matter what set of special characters you set MYVAR to, as long as it's used within single quotes, you shouldn't get any errors parsing it.