Abstract: Some Make topic

An option of c compiler to produce dependency

cc -M main.c

The result is main.o: main.c defs.h

For Sun forte 6, -xM -xM1

Some of automatic variable

$@   the file names of the target of the rule

$% the target menber name, when the target is an archive member

$< the names of the first dependency

$? the names of all the dependencies that are newer than the target,with space between them

$^ the names of all the dependencies, whith spaces between them

Command Execution

The command is excuted by makeing a new subshell for eachline.

One line is One command

If you want to excute more than one commands in same shell, use ; to separate the commands in online.

For example, cd /usr/bin; ls

Or use \ to split shell command to multiple lines

For example,

cd /usr/bin; \

ls

Use - before the command to ignore errors, or "-i" option when run make

clean:
        -rm -f *.o

Canned Command Sequences

The canned commands is actually a variable, so the name must not confilict with other variable names.

define run-yacc
yacc $(firstword $ˆ)
mv y.tab.c $@
endef

The define directive does not expand.

To use the command sequences, substitute the vaiable into the commands of a rule.

foo.c : foo.y
        $(run-yacc)

Substitution References

It has the form ‘$(var:a=b)’ (or ‘$’)
and its meaning is to take the value of the variable var, replace every a
at the end of a word with b in that value, and substitute the resulting
string.

foo := a.o b.o c.o
bar := $(foo:.o=.c)
sets ‘bar’ to ‘a.c b.c c.c’