Question

I’m writting a Makefile in order to compile Java programs. It looks like this:

#!/bin/bash

LANG=en

CURRENT_EX = hello.java
RUN_CURRENT_EX = for i in `ls *.class`; do java *$\.class ; done

RM  = rm -f 
TRASH = *~ *.class          

ALL = $(RM) $(THRASH)    && \
      javac    $(CURRENT_EX)    

all:    
    $(ALL)                   && \
    $(RUN_CURRENT_EX) 

When I compile a Java Program (let’s say its name is “hello.java”) it works like this. At first, I put in the Linux terminal:

$ javac hello.java

It yelds a file named “Hello.class”, and for executing it I put

$ java Hello

The issue is that I want to automate this task through a Makefile, and I have a trouble with this line:

RUN_CURRENT_EX = for i in `ls *.class`; do java *$\.class ; done

where it says “java *$.class”. What I want do is to take only the string “Hello” from “Hello.class” filename, but my regex doesn’t work:

$ make all
Error: Could not find or load main class Hello.class
make: *** [all] Error 1

How could I take away the string “.class” from “Hello.class”?

Thanks in advance 🙂

Answer 1

You should really learn about Makefile syntax. Instead of doing things yourself, make actually has a lot of functionality to help you.

As a starter, also remove the incorrect #!/bin/bash from your Makefile…

Then learn about $(wildcard) for matching files,

Pattern substitution $(patsubst %.class,%,$(CLASSES)) to strip the .class postfix,

and pattern rules, such as

%.class: %.java
    javac $<