--- Makefile.orig	2025-06-01 19:24:24 UTC
+++ Makefile
@@ -1,14 +1,30 @@
-CC=gcc
-CFLAGS=-g -Wall -O2 -Wno-unused-function -Wno-format
-BINDIR=/usr/local/bin
+# Respect user's build environment by using ?= to set defaults for variables
+# not set in the env or make arguments.  Use += to add essential args.
+ 
+CC	?= gcc
+CFLAGS	?= -g -Wall -O2
+CFLAGS	+= -Wno-unused-function -Wno-format
+LDFLAGS	+= -lz -lm
+PREFIX	?= /usr/local
+STRIP	?= strip
+BINDIR=	$(PREFIX)/bin
 
-all:seqtk
+MKDIR	?= mkdir
+INSTALL	?= install
 
-seqtk:seqtk.c khash.h kseq.h
-		$(CC) $(CFLAGS) seqtk.c -o $@ -lz -lm
+all: seqtk
 
-install:all
-		install seqtk $(BINDIR)
+seqtk: seqtk.c khash.h kseq.h
+	$(CC) $(CFLAGS) seqtk.c -o $@ $(LDFLAGS)
 
+# Add DESTDIR staged install support
+# DESTDIR is empty by default to install straight to PREFIX
+install: all
+	$(MKDIR) -p $(DESTDIR)$(BINDIR)
+	$(INSTALL) -c -m 0755 seqtk $(DESTDIR)$(BINDIR)
+
+install-strip: install
+	$(STRIP) $(DESTDIR)$(BINDIR)/seqtk
+
 clean:
-		rm -fr gmon.out *.o ext/*.o a.out seqtk trimadap *~ *.a *.dSYM session*
+	rm -fr gmon.out *.o ext/*.o a.out seqtk trimadap *~ *.a *.dSYM session*