Remove item from a Makefile variable

gnu-makemakefilevariables

I have a makefile, which includes several other makefiles, which in turn all add to a variable like this:

VAR := Something SomethingElse
VAR += SomeOtherThing

(...)

Now I wish to remove SomethingElse from the VAR variable. What do I put in place of (...) to do this?

I am using GNU Make, and a GNU Make specific solution will be fine.

Best Answer

You could use the filter-out text function if you're using GNU Make.

OTHERVAR := $(filter-out SomethingElse,$(VAR))

Related Solutions

Bash – How to trim whitespace from a Bash variable

A simple answer is:

echo "   lol  " | xargs

Xargs will do the trimming for you. It's one command/program, no parameters, returns the trimmed string, easy as that!

Note: this doesn't remove all internal spaces so "foo bar" stays the same; it does NOT become "foobar". However, multiple spaces will be condensed to single spaces, so "foo bar" will become "foo bar". In addition it doesn't remove end of lines characters.

The difference between the GNU Makefile variable assignments =, ?=, := and +=

Lazy Set

VARIABLE = value

Normal setting of a variable, but any other variables mentioned with the value field are recursively expanded with their value at the point at which the variable is used, not the one it had when it was declared

Immediate Set

VARIABLE := value

Setting of a variable with simple expansion of the values inside - values within it are expanded at declaration time.

Lazy Set If Absent

VARIABLE ?= value

Setting of a variable only if it doesn't have a value. value is always evaluated when VARIABLE is accessed. It is equivalent to

ifeq ($(origin VARIABLE), undefined)
  VARIABLE = value
endif

See the documentation for more details.

Append

VARIABLE += value

Appending the supplied value to the existing value (or setting to that value if the variable didn't exist)