CODEWITHSUNDEEP
makefilegnu-make
Swiss Frank
Swiss Frank

Reputation: 2422

make/gmake: given a variable starting with multiple ../, create a variable with one less ../

Given a variable, how can I create another variable with the leading repetitions of ../ that the first variable starts with, albeit with one less repetition?

For instance, given ../../../foo/bar, how do I end up with ../../?

I've tried a perl regexp like perl -e '$a = "../../../foo/bar"; $a =~ /^\.\.\/((\.\.\/)+)/; print "$1\n"' but can't figure out the magic incantation of quotes, backslashes, dollar signs, and so on needed to run it within $(shell).

Further I suspect there's a simpler way to do it.

Upvotes: 0

Views: 44

Answers (1)

Vroomfondel
Vroomfondel

Reputation: 2898

This will remove one ../ at the front: $(patsubst ../%,%,$(ORIGINAL_PATH))

To isolate the first streak of ../ one could go as follows:

space := $(strip) $(strip)#
FIRST_STREAK := $(firstword $(subst $(space)../,../,$(subst ../,../$(space),$(ORIGINAL_PATH))))

Let's write this as a function:

space := $(strip) $(strip)#
UP_PATH = $(patsubst ../%,%,$(firstword $(subst $(space)../,../,$(subst ../,../$(space),$1))))

Test it:

ORIGINAL_PATH := ../../../foo/bar/../baz
$(info $(call UP_PATH,$(ORIGINAL_PATH)))

Output:

../../

Upvotes: 1

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