Sometimes a target does not mean a file but it might represent an action to be performed. When a target  is not related to a file it is called phony target.

For instance:

getobj:
	mv obj/*.o .  2>/dev/null

getobj target move all files with .o extension from obj directory to current directory — not a big deal. However, you should be asking yourself: “What if there is no file in obj ?” That is a good question. In that case, the mv command would return an error that would be passed to the make command.

Note: make command default behavior is to abort the processing when an error is detected while executing commands in rules.

Of course, there will be situations that the obj directory will be empty. How will you avoid the make command from aborting when an error happens?

You can use a special character - (minus) preceding the mv command. Thus:

getobj:
	-mv obj/*.o .  2>/dev/null

- Tells the make to ignore errors. There is another special character: @ – Tells make not to print the command to standard output before executing. You can combine both always preceding the command:

getobj:
	-@mv obj/*.o .  2>/dev/null

There is a special phony target called all where you can group several main targets and phony targets. all phony target  is often used to lead make command while reading makefile.

For instance:

all: getobj app install putobj

The make command will execute the targets in sequence: getobj, app, install and putobj.

Another interesting feature, make command supports is the concept of MACRO in makefiles. We can define a MACRO by writing:

MACRONAME=value

and access the value of MACRONAME by writing either $(MACRONAME) or ${MACRONAME}.

For instance:

EXECPATH=./bin

INCPATH=./include

OBJPATH=./obj

CC=cc

CFLAGS=-g -Wall -I$(INCPATH)

While executing, make replaces $(MACRONAME) with the appropriated definition. Now we know what phony targets and macros are we can move to the next sample.