CODEWITHSUNDEEP
makefile
Guy
Guy

Reputation: 43

Strange behavior of makefile functions

im having issues with $(foreach..) and echo functions. im trying to iterate over a variable and append it into a file.

here is my code:

vars = a b c d
all:
    @$(foreach var, $(vars), echo $(var) >> variables.txt)

the generated file looks like

a echo  b echo c echo d

i have no idea why it prints also the word "echo" and why it is on the same line.

Im working on Windows, on linux the results are as expected.

what am i missing here?

thanks.

Upvotes: 0

Views: 59

Answers (1)

Beta
Beta

Reputation: 99172

Funny thing about output redirection. You can put it at the end of a command:

echo a b c >> filename

Or in the middle of a command:

echo a b >> filename c

Or in multiple places:

echo a >> filename b >> filename c >> filename

and it does exactly the same thing.

In your makefile, this:

$(foreach var, $(vars), echo $(var) >> variables.txt)

is a Make iteration. (The shell has no such command as foreach), and it expands into this:

echo a >> variables.txt echo b >> variables.txt echo c >> variables.txt echo d >> variables.txt

which, as we've seen, is equivalent to:

echo a echo b echo c echo d >> variables.txt

So the shell dutifully echoes a echo b echo c echo d and redirects it to variables.txt.

EDIT: The simplest way to get the effect you want is to add a semicolon:

vars = a b c d
all:
    @$(foreach var, $(vars), echo $(var) >> variables.txt;)

Upvotes: 1

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