Add install rule to Makefile.

src/Makefile

@@ -4,10 +4,11 @@ CC	= cc
 CFLAGS	= -Wall -O2
 LDFLAGS = -static
 LDLIBS	=
-PREFIX = /usr/local/bin/
+PREFIX = /usr/local/
 DESTDIR = 
+BIN = echo yes true false cat
 
-all: echo  yes true false cat
+all: ${BIN}
 echo: echo.c
 wc: wc.c
 yes: yes.c
@@ -16,9 +17,15 @@ false:
 	ln -s true false
 cat: cat.c
 
+install: all
+	install -Dm0775 ${BIN} ${DESTDIR}${PREFIX}bin
+
 clean: 
 	rm echo true  yes false cat
 
 .SUFFIXES: .c .o
 .c.o:
 	${CC} ${CFLAGS} ${LDFLAGS} -c $<
+
+:
+	echo hello