In GNU Make, how do I convert a variable to lower case?

Question

This is a silly question, but.... with GNU Make:

VAR = MixedCaseText
LOWER_VAR = $(VAR,lc)

default:
        @echo $(VAR)
        @echo $(LOWER_VAR)

In the above example, what's the correct syntax for converting VAR's contents to lower case? The syntax shown (and everything else I've run across) result in LOWER_VAR being an empty string.

Answer 1

you can always spawn off tr

LOWER_VAR = `echo $(VAR) | tr A-Z a-z`

or

LOWER_VAR  = $(shell echo $(VAR) | tr A-Z a-z)

The 'lc' functions you trying to call is from GNU Make Standard Library

Assuming that is installed , the proper syntax would be

LOWER_VAR  = $(call lc,$(VAR))

Answer 2

You can do this directly in gmake, without using the GNU Make Standard Library:

lc = $(subst A,a,$(subst B,b,$(subst C,c,$(subst D,d,$(subst E,e,$(subst F,f,$(subst G,g,$(subst H,h,$(subst I,i,$(subst J,j,$(subst K,k,$(subst L,l,$(subst M,m,$(subst N,n,$(subst O,o,$(subst P,p,$(subst Q,q,$(subst R,r,$(subst S,s,$(subst T,t,$(subst U,u,$(subst V,v,$(subst W,w,$(subst X,x,$(subst Y,y,$(subst Z,z,$1))))))))))))))))))))))))))

VAR = MixedCaseText
LOWER_VAR = $(call lc,$(VAR))

all:
        @echo $(VAR)
        @echo $(LOWER_VAR)

It looks a little clunky, but it gets the job done.

If you do go with the $(shell) variety, please do use := instead of just =, as in LOWER_VAR := $(shell echo $VAR | tr A-Z a-z). That way, you only invoke the shell one time, when the variable is declared, instead of every time the variable is referenced!

Hope that helps,

Eric Melski