What does the $$ mean?

[leetow2003]

I read a Makefile,look:

Code: Select all

dep:
	(for i in init/*.c;do echo -n "init/";gcc -M $$i;done) >> tmp_make
	cp tmp_make Makefile

if I write a shell script using the same codes,I find the $$i must be replaced
by $i,why?I want to know what the $$ means?

[Combuster]

What does $ mean to make?

[iansjack]

In this instance, do you want the command interpreter to see the value of $i, or do you want it to see "$i"?

[kohlrak]

I read a Makefile,look:

Code: Select all

dep:
	(for i in init/*.c;do echo -n "init/";gcc -M $$i;done) >> tmp_make
	cp tmp_make Makefile

if I write a shell script using the same codes,I find the $$i must be replaced
by $i,why?I want to know what the $$ means?

I'm not 100% sure, but it could be that $$ is a makefile escape for $, while in shells $$ represents the process ID.