how to prevent “directory already exists error” in a makefile when using mkdir

Question

I need to generate a directory in my makefile and I would like to not get the \"directory already exists error\" over and over even though I can easily ignore it.

I

Answer 1

Looking at the official make documentation, here is a good way to do it:

OBJDIR := objdir
OBJS := $(addprefix $(OBJDIR)/,foo.o bar.o baz.o)

$(OBJDIR)/%.o : %.c
    $(COMPILE.c) $(OUTPUT_OPTION) $<

all: $(OBJS)

$(OBJS): | $(OBJDIR)

$(OBJDIR):
    mkdir -p $(OBJDIR)

You should see here the usage of the | pipe operator, defining an order only prerequisite. Meaning that the $(OBJDIR) target should be existent (instead of more recent) in order to build the current target.

Note that I used mkdir -p. The -p flag was added compared to the example of the docs. See other answers for another alternative.

Answer 2

It works under mingw32/msys/cygwin/linux

ifeq "$(wildcard .dep)" ""
-include $(shell mkdir .dep) $(wildcard .dep/*)
endif

Answer 3

ifeq "$(wildcard $(MY_DIRNAME) )" ""
  -mkdir $(MY_DIRNAME)
endif

Answer 4

A little simpler than Lars' answer:

something_needs_directory_xxx : xxx/..

and generic rule:

%/.. : ;@mkdir -p $(@D)

No touch-files to clean up or make .PRECIOUS :-)

If you want to see another little generic gmake trick, or if you're interested in non-recursive make with minimal scaffolding, you might care to check out Two more cheap gmake tricks and the other make-related posts in that blog.

Answer 5

On UNIX Just use this:

mkdir -p $(OBJDIR)

The -p option to mkdir prevents the error message if the directory exists.

Answer 6

On Windows

if not exist "$(OBJDIR)" mkdir $(OBJDIR)

On Unix | Linux

if [ ! -d "$(OBJDIR)" ]; then mkdir $(OBJDIR); fi