Can I obtain just the second prerequisite in GNU make?

Question

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How to get the second dependency file using Automatic Variables in a Makefile?

I am using GNU make, and I'm using automatic variables such at $<, $^ etc. I know that $< is just the first prerequisite, and $^ is all the prerequisites. Is there a way to obtain just the second prerequisite?

Could you say a little more about why you need this, or what you're trying to accomplish? You might be able to pick apart `$^` element by element (i.e. treat it as an array), and then grab the second that way. — Phil Miller, Sep 05 '12 at 15:24
@Beta, Yep - this is a duplicate. I'll vote to close it as such. — pauldoo, Sep 07 '12 at 12:44

score 91 · Accepted Answer · edited Nov 24 '22 at 05:19

91

Assuming your prerequisites are regular tokens,

echo $(word 2,$^)

I often find myself giving the first argument a special position, and accessing the remaining prerequisites with

echo $(filter-out $<,$^)

*Though sometimes with the upper solution you might find repeating elements.

edited Nov 24 '22 at 05:19

pandaero

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answered Sep 05 '12 at 15:27

tripleee

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The filter-out trick is exactly what I was looking for :) – vbwx Nov 01 '17 at 13:43

score 0 · Answer 2 · answered Sep 05 '12 at 15:28

0

The best I can come up with, which I feel is a bit of a hack, is to use echo $^ | cut -f2 -d' ', à la:

output.txt: a.txt b.txt
    cat $< | ./something `echo $^ | cut -f2 -d' '` > $@

I'd love to hear a better answer than this. :)

answered Sep 05 '12 at 15:28

pauldoo

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Here you go: `$(word 2,$^)` – Maxim Egorushkin Sep 05 '12 at 15:30

Can I obtain just the second prerequisite in GNU make?

2 Answers2