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ok makefiles, to start comments are “#”, long line can be split with the “ \”, tab is required after a dependency line, $(VAR) or ${VAR} for variables.

gcc main.c file1.c file2.c -o hello

is what you normaly would run to complile a program with the gcc compiler and the 3 .c file to an executable called hello.

#
# Makefile for hello 
#
# compiler: gcc
# to compile type "make" at command line
#
all :
      gcc main.c file1.c file2.c -o hello

this file is saved with the name “Makefile” and will compile the program hello just as if it was typed out on the command line. things to note - [target]:[dependencies] in this case the target “all” depends on everything. this looks for time stamps to save on compile time. if a dependant has a newer last changed stamp then the taget then the target needs to be recompiled else is left alone.

#
# Makefile for hello 
#
# compiler: gcc
# to compile type "make" at command line
#
all : hello

hello : main.o file1.o file2.o
      gcc main.o file1.o file2.o -o hello
      
main.o : main.c
      echo main.c is being compiled 
      gcc -c main.c

file1.o : file1.c
      echo file1.c is being compiled 
      gcc -c file1.c

file2.o : file2.c
      echo file2.c is being compiled
      gcc -c file2.c

clean : 
      rm -rf *.o hello

this example builds alittle on what was there before. last time if there was a change to one of the files everything was recompiled. breaking everything up as shown here if only file2.c was modified on file2 would be recompiled. the clean: removes any left over executables and object files that are left over. i've also thrown in some simple echos to show that shell commands can be used as well.

#
# Makefile for hello 
#
# compiler: gcc
# to compile type "make" at command line
#

CC = gcc
CFLAGS = -c
OBJ = main.o file1.o file2.o

all : hello

hello : $(OBJ)
      $(CC) $(OBJ) -o hello
      
main.o : main.c
      echo main.c is being compiled 
      $(CC) $(CFLAGS) main.c

file1.o : file1.c
      echo file1.c is being compiled 
      $(CC) $(CFLAGS) main.c

file2.o : file2.c
      echo file2.c is being compiled
      $(CC) $(CFLAGS) file2.c

clean : 
      rm -rf *.o hello

in this extension of the makefile i added variables for everything that repeated throughout the file so that if i wanted to change lets say the compiler all i would have to do is change the CC value at the top.

Makefile documentation

NOTE: this documentation is located in two places Makefile basics

if you add to this one please add to the other one as well.