How to Pass Variables to Makefile

[Chakkarapani]

Hi, I want to know how to pass a variable to makefile from the command prompt. And inside the makefile i want to check this variable and do conditional compilation.
In the command prompt when i just call make i starts executing blindly and no variables i passing for this make. But i need an option like to conditionally compile upon users choice.Please tell me how to establish this.

[VK2COT]

Hello,

You did not specify if you are using
GNU make or standard HP-UX.

Several possibilities:

a) For example, in a properly written
Makefile, the variable CFLAGS is included
in each command that runs the C compiler,
so a file myfile.c would be compiled as:

# cc -c $(CFLAGS) myfile.c

Whatever value is set for CFLAGS, it affects
each compilation.

When you run make, you can override it.

For example

# make CFLAGS='-g -O'

b) In HP-UX, there is make(1) flag "-e":

Environment variables override assignments
within Makefiles

c) HP-UX make(1) supports ifdef
test in Makefile. An example:

ifdef UNAME
SYSTEM = $(UNAME)
else
SYSTEM = "UNSUPPORTED"
endif

Cheers,

VK2COT

[Dennis Handly]

>And inside the makefile i want to check this variable and do conditional compilation.

As VK2COT alluded, you can't do this with HP's make, you must use gmake.

>But i need an option like to conditionally compile upon users choice.

You might be able to do this by explicitly mentioning a target. This allows you to build only parts of the makefile.

>VK2COT: c) HP-UX make(1) supports ifdef
test in Makefile.

I'm not sure where you got this but it isn't in the man page.

The only new feature I see is "conditional macro definition" but this probably won't help.

[Steven Schweda]

> I'm not sure where you got this but it
> isn't in the man page.

Nor, apparently, in reality:

dyi # cat makefile
ifdef UNAME
SYSTEM = $(UNAME)
else
SYSTEM = "UNSUPPORTED"
endif

dyi # make
Make: Must be a separator on rules line 2. Stop.

dyi # gmake
gmake: *** No targets. Stop.

dyi # uname -a
HP-UX dyi B.11.31 U ia64 4235313755 unlimited-user license

[VK2COT]

Hello,

Ahh, wrong statement by me (option c) in previous post).

GNU make supports two types of If test, ifdef
and ifeq (and the negative versions ifndef,
ifneq), not the HP-UX native one!

gmake != HP-UX make

Cheers,

VK2COT