Conditional Parts of Makefiles

Example of a Conditional

    libs_for_gcc = -lgnu
  normal_libs =

  ifeq ($(CC),gcc)
    libs=$(libs_for_gcc)
  else
    libs=$(normal_libs)
  endif

  foo: $(objects)
          $(CC) -o foo $(objects) $(libs)

Syntax of Conditionals

The syntax of a simple conditional with no else is as follows:

conditional-directive
text-if-true
endif

The text-if-true may be any lines of text, to be considered as part of the makefile if the condition is true. If the condition is false, no text is used instead.

The syntax of a complex conditional is as follows:

conditional-directive
text-if-true
else
text-if-false
endif

or:

conditional-directive
text-if-one-is-true
else conditional-directive
text-if-true
else
text-if-false
endif

Conditional-directive

ifeq, ifneq, ifdef, and ifndef

ifeq (arg1, arg2)

ifeq 'arg1' 'arg2'

ifeq "arg1" "arg2"

ifeq "arg1" 'arg2'

ifeq 'arg1' "arg2"

ifneq (arg1, arg2)

ifneq 'arg1' 'arg2'

ifneq "arg1" "arg2"

ifneq "arg1" 'arg2'

ifneq 'arg1' "arg2"

ifdef variable-name

ifndef variable-name