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I want to write something along these lines:
$(foreach (var1, var2), ($(LIST1), $(LIST2)), cp $(var1) $(var2);)
How do I go about doing this in a GNU makefile?
365
Yes, I can declare multiple variables in a for-loop. And you, too, can now declare multiple variables, in a for-loop, as follows: Just separate the multiple variables in the initialization statement with commas. Do not forget to end the complete initialization statement with a semicolon.
Yes, by using the comma operator. E.g. for (i=0, j=0; i<10; i++, j++) { ... }
6.6 Appending More Text to Variables Often it is useful to add more text to the value of a variable already defined. You do this with a line containing ' += ', like this: objects += another.o.
If you want a string to have a dollar sign, you can use $$ . This is how to use a shell variable in bash or sh . Note the differences between Makefile variables and Shell variables in this next example.
Beta's suggestion to use join is on the right track, but the problem is that it's not so easy to use it in a way that constructs a command line containing whitespace, such as the one you originally wanted:
$(foreach (var1, var2), ($(LIST1), $(LIST2)), cp $(var1) $(var2);)
because join joins words together: it was originally intended for constructing filenames. However you can play a trick; here's an example of a way to use join that gives you the output you are looking for:
$(subst ^, ,$(join $(addprefix cp^,$(LIST1)),$(patsubst %,^%;,$(LIST2))))
If you think your lists might contain ^ characters then choose something else. Let me know if you need this unpacked/explained.
136
LIST1 := a b c
LIST2 := 1 2 3
# outside a rule:
$(foreach var1, a b c, $(foreach var2, 1 2 3, $(info $(var1)_$(var2))))
# inside a rule: first line starts with a TAB, all the rest are spaces
all:
@for x in $(LIST1);\
do \
for y in $(LIST2);\
do\
echo $$x $$y; \
done \
done
(Please note that a nested loop that does cp doesn't make much sense.)
EDIT:
Well why didn't you say so?
LIST3 := $(join $(LIST1),$(LIST2))
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