Using make

You have probably already found out that compiling, packing, and signing of Place Users can become a little tedious, repeated every time you change any tiny bit in the source code. In order to make life easier you can write a shell script that cares for all the necessary steps. This solution has a drawback: A shell script will usually try to recompile everything although you only changed one class. This takes too much time when your projects become larger. Here make may be quite a handy tool. It checks the timestamps and only calls the compiler for modified files.

How do I write a makefile for a Place User? We show you for the case of the HelloWorld agent:

# Caution: --> must be replaced by a TAB sign

all: HelloWorld.spu

clean:
-->rm -f *.class *.spu

rebuild: clean all

HelloWorld.class: HelloWorld.java
-->javac -classpath $(CLASSPATH):. HelloWorld.java

HelloWorld.spu: HelloWorld.class
-->rm -f HelloWorld.spu
-->secadmin /home/user/ametas/places/first/config crspu HelloWorld
-->secadmin /home/user/ametas/places/first/config addsig HelloWorld -privk /home/user/ametas/id/user.idy

This makefile must be stored in the same directory as the HelloWorld agent. To execute it, change to this directory (here e.g. $AMETAS_HOME/agents) and call the program make:

cd $AMETAS_HOME/agents
make

All dependencies and target files behind all (here HelloWorld.spu) will be updated if necessary. To remove all classes and SPU containers in the current directory you use

make clean

This processes the clean rule, resulting in some rm command executions. The rebuild rule at first deletes all automatically generated files (clean) and then recompiles all files (all):

make rebuild

A short explanation of make

make processes makefiles containing rules which define dependencies between files of a project. A rule consists of a target and zero or more dependencies. Thus, the rule HelloWorld.class: HelloWorld.java (from the above makefile) declares that the file HelloWorld.class (the target) depends on the file HelloWorld.java. That means that HelloWorld.class must always be rebuild whenever HelloWorld.java has changed (has a newer timestamp than HelloWorld.class). The way how to create HelloWorld.class is displayed in the next line. In this example the Java compiler is started on the Java file. Each command that appears in a rule must be preceded by a tabulator, not by a blank! Otherwise it will not be executed. Note that we used --> in the example to symbolize TABs; you have to hit your TAB key instead.

Rules may contain several commands. You find an example with the rule for HelloWorld.spu: HelloWorld.class. When you call make without arguments, it looks for a file named Makefile or makefile in the current working directory and tries the first rule (here all). This leads to the following actions:

1. make analyzes the rule for the target all and finds out that it depends on HelloWorld.spu.
2. Since there is a rule for HelloWorld.spu, this rule is now analyzed in order to create HelloWorld.spu.
3. The HelloWorld.spu rule says that the target depends on HelloWorld.class. Now a rule is searched for this file.
4. HelloWorld.class depends on HelloWorld.java, but HelloWorld.java does not offer further rules. When HelloWorld.class either does not exist or is older than HelloWorld.java, the command defined by this rule will be executed in order to create or update HelloWorld.class.
5. make now turns back to the rule for HelloWorld.spu. If the file HelloWorld.class was recreated, it is now younger than HelloWorld.spu, and the commands to create HelloWorld.spu are executed in order to update HelloWorld.spu. The SPU is removed at first, then created and signed. This rule consists of three commands: The first one remove the outdated SPU file; the second recreates the SPU; the third one signs it. The third command is pretty long and therefore split in two parts. You need to add a backslash behind every line that is continued by the next line.

Ask yourself what happens when HelloWorld.class is younger than HelloWorld.java and HelloWorld.spu does not exist. For more details on make and Makefiles please refer to their documentation which is normally part of every Unix distribution.