To show an image file to X,
showimg::
<TAB>qiv -mtf *png
Also you can call any rule like this.
$ make rule2
when you have two lines like this anywhere in the makefile.
rule2::
<TAB>echo "Rule 2"
-Girish
On Fri, Jun 18, 2010 at 4:59 PM, Girish Venkatachalam
<girishvenkatachalam@xxxxxxxxx> wrote:
Dear all,
This mail is an attempt to teach makefiles in UNIX. Makefiles work the
same way everywhere even in
Windoze. There are also several names for the make tool. tmake, pmake,
gmake, nmake and so on. ;)
But all of them work similarly.
In the BSD world makefiles are more subtle and much shorter. Makefiles
also work differently in the
autoconf world with configure script, Makefile.in , Makefile.am and so on.
As you can see it is very complicated, complex and needlessly boring. But
this does not take away the fact that makefiles are a beautiful thing.
I shall try to illustrate this idea in this mail.
$ make
will try to execute the first rule in the makefile found in the
current directory.
makefile can be named "makefile" or "Makefile" or "MAKEFILE".
But it almost always is named "Makefile".
A makefile is organized as
rule :: dependency.c dependency.h foo.c ba.c
<TAB>gcc foo.c ba.c dependency.c -o rule
I think you get the idea.
rule name is also the target name.
In other words, you tell the makefile or in essence the make utility that
?to create the target "rule" you need to execute the line given with
a <TAB> character
?directly below the rule line.
And you also tell makefile that whenever any of the files
"dependency.c dependency.h foo.c ba.c"
change the target has to be updated.
In other words make helps you keep your targets up-to-date.
But all these are academic words without much meaning to hackers.
So let me now talk in practical lingo.
If you wish to create a mp3 file from a bunch of wav files or
?if you wish to dump a file an image file, you can write rules like these.
out.mp3 : in.wav
<TAB>ffmpeg -i in.wav out.mp3
You can also call it like this.
createmp3: in.wav
<TAB>ffmpeg -i in.wav out.mp3
The rule name need not correspond to the target file created.
It is just a name after all like Girish.
And the dependencies can be nil too.
clean::
<TAB>rm -rf *.o
will remove all the object files unilaterally.
Makefiles are a very powerful UNIX "power tool" and it takes a lot of
experience and
knowledge to use it effectively.
I have not been using it well yet.
But remember that there are makefile variables, shell variables,
makefile if conditions
and while loops ?and they should not interfere with shell's if and while .
If you wish to write a shell script like this.
$ for file in `ls /etc/`
? do
? ? ? ?echo $file
? done
in a Makefile they have to be written like this.
printfilesinetc::
? ? ? for file in `ls /etc/`; do \
? ? ? ?echo $$file; \
? ? ? ?done
Reason being that the makefile rule line is exactly that. Just one line.
So if you wish to run multiple commands you need to run like this.
<TAB>cd /etc/ && cat passwd
and if you wish to background processes, you write like this:
? ? ? ? ? (rm -rf /tmp&) && \
? ? ? ? ? echo "started the removal in background"
Also if you wish to avoid echoing of executed rule commands you need
to prefix a @.
printhello::
<TAB>echo "hello"
should actually be
printhello::
<TAB>@echo "hello"
Try it and you will know.
Have fun!
-Girish
--
Gayatri Hitech
web: http://gayatri-hitech.com
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