Few Things about Makefile

I read through this article, http://www.opussoftware.com/tutorial/TutMakefile.htm, today. And wrote down some notes.

target : sources
"The target depends on the sources."
: colon are called dependency lines.

The last-changed time is the time as it appears in the file-system directory = timestamp
if timestamp(target) is earlier than timestamp(sources) then build a new one.

include hearder
main.o : main.c def.h
io.o : io.c def.h
or
main.o io.o : def.h

Shell Lines

• the  indented lines that follow each dependency line are called shell lines, which tell Make how to build the target.
• Make checks the shell line exit status. If the first shell line returning a non-zero exit status, it will stop.
• adding "-" prefix let Make ignore the exit status and continue.

Macros

• macro definition: name = value
• expressions form: $(name) or ${name}
• if the name is a single letter, the parentheses or braces are optional, ex. $X
• defining on the command line:
• make CFLAGS=-ms
• (including spaces) make "CFLAGS=-ms -z -p"
• run-time macros
• .TARGET is the name of the current target
• .SOURCES is the name of the inferred source
• macro modifiers
• $(name, modifier[,modifier ...]), ex. SRCS = $(OBJS,.o=.c)
• filename components, if PATH = /home/heron/test.txt
• D, directory, $(PATH, D) = /home/heron
• E, extensions, $(PATH, E) = .txt
• F, file name, $(PATH, F) = test.txt

Conditional Directives

ex.

%if $(CC) == gcc

        CC = g++

%elif $(CC) == g++

        CC = gcc

%else

        echo "haha"

%endif

For More Info : http://unixhelp.ed.ac.uk/CGI/man-cgi?make