Exercise Hello-World

Objective

Learn how to work with makefiles and make utility (the manual is here) by making a "Hello, world" program.

Check that your filesharing system works.

Introduction

Directory for the exercise

• If you work on Lifa, create the directory for the hello-world-excercise with the command

  mkdir --parents ~/public_html/numeric/hello

  and make the exercise in that directory.

• If you work on your own box create the directory, say "/path_to_numeric/numeric/hello", wherever you find it suitable and then upload/synchronise the "/path_to_numeric/numeric" directory with your filesharing system.

Hints

Tabulator-sign in makefiles in nano-editor

The commands in the makefile must be prefixed with the tabulator-sign (by default) which might not be visible in the nano editor. To make them visible, create a ~/.nanorc file with the content

syntax "makefile" "[Mm]akefile"
color white,magenta " "

(or whatever colors you might prefer) where there is the tabulator sign (obtained by pressing the tabulator-key on the keyboard) between the quotes in the second line.

Another solution is to use GNU Make version 3.82+ (which is installed on lifa as ~efb23/bin/make) where the recipe prefix is controlled by the variable .RECIPEPREFIX. You can then set it to any character, for example ";" with the command

.RECIPEPREFIX := ;

Colors in terminal

It seems that on lifa the default value of the TERM environment variable (which specifies the type of the terminal you are using) is vt100, which is colorless. In order to have colors you have to change the value of this variable to xterm. You have to find out in which file this "vt100" is hiding with the command

grep vt100 .*

and then go to that file and change "vt100" to "xterm". Most probably you will have to do the following:

• On lifa if your shell is csh, place the following line in your ~/.cshrc file (where ~/ is the alias for your home directory)

  setenv TERM xterm

• If your shell is bash, place the following line in your ~/.profile file

  export TERM=xterm

You can find out which shell you run with the command

 ps -p $$ 

or

 echo $0 

If you run csh, but want to run bash, put the following lines into your ~/.login file.

if ( -f /usr/users/efb23/bin/bash ) then
  setenv SHELL /usr/users/efb23/bin/bash
  exec $SHELL --login
endif

Syntax highlighting in nano-editor

If syntax highlighting does not work for you on lifa, you can include (one of) the following lines in your ~/.nanorc file:

include /usr/share/nano/c.nanorc # c-syntax highlighting
include /usr/share/nano/java.nanorc # java-syntax highlighting
include /usr/share/nano/python.nanorc # python-syntax highlighting
include /usr/share/nano/tex.nanorc # tex-syntax highlighting
include /usr/users/efb23/share/nano/fortran.nanorc # fortran-syntax highlighting

Tasks

1. Hello, world

   • Create a project with the corresponding makefile with the following targets:

     1. The (default) target "A" the prerequisite of which is a text file, say out.A.txt, (eventually with the text "hello, your_name"):

        A : out.A.txt

        The file out.A.txt should be built by redirecting the output from a program, say mainA, which prints "hello, your_name" on the standard output:

        out.A.txt : mainA
        	./mainA > out.A.txt

        The mainA program should be built from a mainA.c using the recipe

        
        mainA : mainA.c
        # without an explicit rule here the following implicit rule applies
        # $(LINK.c) $^ $(LDLIBS) -o $@
        

        The matinA.c file should look like this,

        #include<stdio.h>
        int main(){
        	printf("hello, your_user_name\n");
        	return 0;
        } 

        The interpreted languages, like python, would rather run the program via the interpreter,

        
        PYTHON = ~efb23/bin/python3 # python3 version 3.5.1
        out.A.txt : mainA.py
        	$(PYTHON) mainA.py > out.A.txt

        where the mainA.py file should look like this,

        print("hello, your_user_name")

     2. Target "cleanA" (without prerequisites) that removes all generated files leaving only the essential files:

        cleanA :
        	rm -f mainA out.A.txt

   • Make sure commands make A and make cleanA work as intended.

   • Comment an arbitrary line in the makefile explaining its purpose.

2. Check

   Create a "check" targets that check whether the "A" target has been built correctly. For example,

   check: out.A.txt
   	@echo "checking target A ..."
   	@echo "hello, $(shell whoami)" > correct.txt
   	@diff --brief correct.txt out.A.txt
   	@echo "target A seems to be ok ..."
   	@rm -f correct.txt