how to double space text?

[steve%brl-bmd at sri-unix.UUCP]

From:      Stephen Wolff <steve at brl-bmd>

When compiled,
		main(){
			char c;
			while(1){
				putchar(c=getchar());
				if(c=='\n')putchar(c);
			}
		}
works as a filter.  So does

		awk '{print; printf("\n");}'

but neither is blindingly efficient -- except for the programmer.