Create directories using make file

directorymakefileobject

I want to create directories using makefile. My project directory is like this

+--Project  
   +--output  
   +--source  
     +Testfile.cpp  
   +Makefile

I want to put all the objects and output into the respective output folder. I want to create folder structure which would be like this after compiling.

+--Project
   +--output
     +--debug (or release)
       +--objs
         +Testfile.o
       +Testfile (my executable file)
   +--source
     +Testfile.cpp
   +Makefile

I tried with several options, but could not succeed. Please help me to make directories using make file. I'm posting my Makefile for your consideration.

#---------------------------------------------------------------------
# Input dirs, names, files
#---------------------------------------------------------------------
OUTPUT_ROOT := output/

TITLE_NAME := TestProj 

ifdef DEBUG 
    TITLE_NAME += _DEBUG
else
ifdef RELEASE
    TITLE_NAME += _RELEASE
endif
endif


# Include all the source files here with the directory tree
SOURCES := \
        source/TestFile.cpp \

#---------------------------------------------------------------------
# configs
#---------------------------------------------------------------------
ifdef DEBUG
OUT_DIR     := $(OUTPUT_ROOT)debug
CC_FLAGS    := -c -Wall
else
ifdef RELEASE
OUT_DIR     := $(OUTPUT_ROOT)release
CC_FLAGS    := -c -Wall
else
$(error no build type defined)
endif
endif

# Put objects in the output directory.
OUT_O_DIR   := $(OUT_DIR)/objs

#---------------------------------------------------------------------
# settings
#---------------------------------------------------------------------
OBJS = $(SOURCES:.cpp=.o)
DIRS = $(subst /,/,$(sort $(dir $(OBJS))))
DIR_TARGET = $(OUT_DIR)

OUTPUT_TARGET = $(OUT_DIR)/$(TITLE_NAME)

CC_FLAGS +=   

LCF_FLAGS := 

LD_FLAGS := 

#---------------------------------------------------------------------
# executables
#---------------------------------------------------------------------
MD := mkdir
RM := rm
CC := g++

#---------------------------------------------------------------------
# rules
#---------------------------------------------------------------------
.PHONY: all clean title 

all: title 

clean:
    $(RM) -rf $(OUT_DIR)

$(DIR_TARGET):
    $(MD) -p $(DIRS)

.cpp.o: 
    @$(CC) -c $< -o $@

$(OBJS): $(OUT_O_DIR)/%.o: %.cpp
    @$(CC) -c $< -o $@

title: $(DIR_TARGET) $(OBJS)

Best Answer

In my opinion, directories should not be considered targets of your makefile, either in technical or in design sense. You should create files and if a file creation needs a new directory then quietly create the directory within the rule for the relevant file.

If you're targeting a usual or "patterned" file, just use make's internal variable $(@D), that means "the directory the current target resides in" (cmp. with $@ for the target). For example,

$(OUT_O_DIR)/%.o: %.cpp
        @mkdir -p $(@D)
        @$(CC) -c $< -o $@

title: $(OBJS)

Then, you're effectively doing the same: create directories for all $(OBJS), but you'll do it in a less complicated way.

The same policy (files are targets, directories never are) is used in various applications. For example, git revision control system doesn't store directories.

Note: If you're going to use it, it might be useful to introduce a convenience variable and utilize make's expansion rules.

dir_guard=@mkdir -p $(@D)

$(OUT_O_DIR)/%.o: %.cpp
        $(dir_guard)
        @$(CC) -c $< -o $@

$(OUT_O_DIR_DEBUG)/%.o: %.cpp
        $(dir_guard)
        @$(CC) -g -c $< -o $@

title: $(OBJS)

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For older versions of Python, I see two answers with good qualities, each with a small flaw, so I will give my take on it:

Try os.path.exists, and consider os.makedirs for the creation.

import os
if not os.path.exists(directory):
    os.makedirs(directory)

As noted in comments and elsewhere, there's a race condition – if the directory is created between the os.path.exists and the os.makedirs calls, the os.makedirs will fail with an OSError. Unfortunately, blanket-catching OSError and continuing is not foolproof, as it will ignore a failure to create the directory due to other factors, such as insufficient permissions, full disk, etc.

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Alternatively, there could be a second os.path.exists, but suppose another created the directory after the first check, then removed it before the second one – we could still be fooled.

Depending on the application, the danger of concurrent operations may be more or less than the danger posed by other factors such as file permissions. The developer would have to know more about the particular application being developed and its expected environment before choosing an implementation.

Modern versions of Python improve this code quite a bit, both by exposing FileExistsError (in 3.3+)...

try:
    os.makedirs("path/to/directory")
except FileExistsError:
    # directory already exists
    pass

...and by allowing a keyword argument to os.makedirs called exist_ok (in 3.2+).

os.makedirs("path/to/directory", exist_ok=True)  # succeeds even if directory exists.

Best Answer

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