Re: a for-loop-like function

[Tristan Van Berkom]

Chien-Lung Wu wrote:

> Hi, 
>
>         I have a question about writing Makefile. Could any one help me.
>
> Question:
>         As I do my project using gnu make, I have  sub_directories and I
> would like the files/directories under these subdirectories been compiled.
>
>         Therefore I create a makefile as follows:
>
>         SUB_DIRS = src vlan ip lib    # (I have 4 subdirs-- src, vlan, ip,
> and lib)
>
> 	all: 
> 		for subdir  in $(SUBDIRS) ; do \
>                         make -C $subdir; \
>                 done;
>
>
>         So that I can "make -C" to each sub-directory and get them compiled.
>         However, Make utility seems can not support this kind of for-loop.
>
>         Are there any way in make utility to get this for-loop done?
>  
firstly,
   If you need to access a shell variable, you'll need to pass a `$' to 
the shell.
To do so, you'll need to escape it with an additional `$' like so:

   make -C $$subdir;

Furthermore, (as discussed in another mail on this list just today),
you will loose any exit value from the sub-make, if you wish to
trap the errors you should at least do this:

   make -C $$subdir || exit -1;

read:
      http://mail.gnu.org/archive/html/help-make/2003-09/msg00028.html
for something a little more scalable.

Cheers,
                              -Tristan