Re: clear command in makefile..

[Dave Seaman]

On 1 Jul 2006 09:37:59 -0700, silversurfer wrote:
> Hello world,
> I was just wondering why the clear-line in my Makefile does not work:

> main:main.o $(ADDOBJS)
>          clear
>          @g++ -o main $(LDFLAGS) $+



> As far as I understood it, it should be possible to add multiple
> shell-commands.. Nevertheless, this does compile the files, but the
> 'clear' before does not work..

> Anyone knows why?

> PS I would like to use this because I like having a clean screen with
> the actual errors on it.. for me, it is easier... ;)

The "clear" command actually does work, but it's not necessarily the
first thing that gets generated when you run "make".  It only gets
generated when that particular rule is applied, and that rule is not what
causes the program to be compiled.

You can type "make -n" to have the generated sequence of commands echoed
to the screen without being executed.

If you have, say, a main.cc file plus a Makefile containing exactly those
three lines quoted above, you will see the following:

$ make -n 
g++    -c -o main.o main.cc
clear
g++ -o main  main.o


The reason for this is that you didn't actually specify a compile command
in your Makefile, but only a link command.  You said "main" depends on
"main.o", but you didn't give a rule for generating "main.o".  The "make"
program supplied the compile command for you from its implicit rulebase,
thus generating "main.o" for you.  Once the prerequisite (main.o) was
satisfied, "make" was able to proceed by applying your rule for the
link step.


-- 
Dave Seaman
U.S. Court of Appeals to review three issues 
concerning case of Mumia Abu-Jamal.
<http://www.mumia2000.org/>