OS detecting makefile

Question

I routinely work on several different computers and several different operating systems  which are Mac OS X  Linux  or Solaris  For the project I m working on  I pull my code from a remote git repository   I like to be able to work on my projects regardless of which terminal I m at  So far  I ve found ways to get around the OS changes by changing the makefile every time I switch computers  However  this is tedious and causes a bunch of headaches   How can I modify my makefile so that it detects which OS I m using and modifies syntax accordingly   Here is the makefile   cc   gcc -g CC   g   -g yacc   YACC  lex   FLEX   all  assembler  assembler  y tab o lex yy o           CC  -o assembler y tab o lex yy o -ll -l y  assembler o  assembler c           cc  -o assembler o assembler c  y tab o  assem y           yacc  -d assem y           CC  -c y tab c  lex yy o  assem l           lex  assem l           cc  -c lex yy c  clean          rm -f lex yy c y tab c y tab h assembler   o   tmp   debug   acts

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The uname command  http   developer apple com documentation Darwin Reference ManPages man1 uname 1 html  with no parameters should tell you the operating system name   I d use that  then make conditionals based on the return value   Example  UNAME      shell uname   ifeq    UNAME   Linux    do something Linux-y endif ifeq    UNAME   Solaris    do something Solaris-y endif

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That s the job that GNU s automake autoconf are designed to solve  You might want to investigate them   Alternatively you can set environment variables on your different platforms and make you Makefile conditional against them

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The git makefile contains numerous examples of how to manage without autoconf automake  yet still work on a multitude of unixy platforms

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I was recently experimenting in order to answer this question I was asking myself  Here are my conclusions   Since in Windows  you can t be sure that the uname command is available  you can use gcc -dumpmachine  This will display the compiler target   There may be also a problem when using uname if you want to do some cross-compilation   Here s a example list of possible output of gcc -dumpmachine    mingw32 i686-pc-cygwin x86 64-redhat-linux   You can check the result in the makefile like this   SYS      shell gcc -dumpmachine  ifneq      findstring linux    SYS       Do Linux things else ifneq     findstring mingw    SYS       Do MinGW things else ifneq     findstring cygwin    SYS       Do Cygwin things else    Do things for others endif   It worked well for me  but I m not sure it s a reliable way of getting the system type  At least it s reliable about MinGW and that s all I need since it does not require to have the uname command or MSYS package in Windows   To sum up  uname gives you the system on which you re compiling  and gcc -dumpmachine gives you the system for which you are compiling

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There are many good answers here already  but I wanted to share a more complete example that both    doesn t assume uname exists on Windows  also detects the processor   The CCFLAGS defined here aren t necessarily recommended or ideal  they re just what the project to which I was adding OS CPU auto-detection happened to be using   ifeq    OS  Windows NT      CCFLAGS    -D WIN32     ifeq    PROCESSOR ARCHITEW6432  AMD64          CCFLAGS    -D AMD64     else         ifeq    PROCESSOR ARCHITECTURE  AMD64              CCFLAGS    -D AMD64         endif         ifeq    PROCESSOR ARCHITECTURE  x86              CCFLAGS    -D IA32         endif     endif else     UNAME S      shell uname -s      ifeq    UNAME S  Linux          CCFLAGS    -D LINUX     endif     ifeq    UNAME S  Darwin          CCFLAGS    -D OSX     endif     UNAME P      shell uname -p      ifeq    UNAME P  x86 64          CCFLAGS    -D AMD64     endif     ifneq    filter  86   UNAME P             CCFLAGS    -D IA32     endif     ifneq    filter arm    UNAME P             CCFLAGS    -D ARM     endif endif

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Note that Makefiles are extremely sensitive to spacing  Here s an example of a Makefile that runs an extra command on OS nbsp X and which works on OS nbsp X and Linux  Overall  though  autoconf automake is the way to go for anything at all non-trivial   UNAME      shell uname -s  CPP   g   CPPFLAGS   -pthread -ansi -Wall -Werror -pedantic -O0 -g3 -I  nexopia include LDFLAGS   -pthread -L nexopia lib -lboost system  HEADERS   data structures h http client h load h lock h search h server h thread h utility h OBJECTS   http client o load o lock o search o server o thread o utility o vor o  all  vor  clean      rm -f   OBJECTS  vor  vor    OBJECTS        CPP    LDFLAGS  -o vor   OBJECTS  ifeq    UNAME  Darwin        Set the Boost library location     install name tool -change libboost system dylib  nexopia lib libboost system dylib vor endif    o    cpp   HEADERS  Makefile       CPP    CPPFLAGS  -c

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Here s a simple solution that checks if you are in a Windows or posix-like  Linux Unix Cygwin Mac  environment   ifeq    shell echo  check quotes    check quotes      WINDOWS    yes else    WINDOWS    no endif   It takes advantage of the fact that echo exists on both posix-like and Windows environments  and that in Windows the shell does not filter the quotes

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I had a case where I had to detect the difference between two versions of Fedora  to tweak the command-line options for inkscape   - in Fedora 31  the default inkscape is 1 0beta which uses --export-file  - in Fedora  lt  31  the default inkscape is 0 92 which uses --export-pdf  My Makefile contains the following    set VERSION ID from  etc os-release    eval   shell grep VERSION ID  etc os-release      select the inkscape export syntax  ifeq    VERSION ID  31  EXPORT   export-file else EXPORT   export-pdf endif    rule to convert inkscape SVG  drawing  to PDF    pdf     svg     inkscape --export-area-drawing   lt  --  EXPORT       This works because  etc os-release contains a line  VERSION ID  lt value gt    so the shell command in the Makefile returns the string VERSION ID  lt value gt   then the eval command acts on this to set the Makefile variable VERSION ID  This can obviously be tweaked for other OS s depending how the metadata is stored   Note that in Fedora there is not a default environment variable that gives the OS version  otherwise I would have used that

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Another way to do this is by using a  configure  script  If you are already using one with your makefile  you can use a combination of uname and sed to get things to work out  First  in your script  do   UNAME uname   Then  in order to put this in your Makefile  start out with Makefile in which should have something like  UNAME   UNAME     in it   Use the following sed command in your configure script after the UNAME uname bit   sed -e  s   UNAME    UNAME    lt  Makefile in  gt  Makefile   Now your makefile should have UNAME defined as desired  If elif else statements are all that s left

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I ran into this problem today and I needed it on Solaris so here is a POSIX standard way to do  something very close to  this     Detect OS UNAME    uname     Build based on OS name DetectOS      - make   UNAME      OS is Linux  use GCC Linux  program c      SHELL VARIABLE  -D LINUX STUFF HERE       rm -f program     gcc   SHELL VARIABLE  -o program program c    OS is Solaris  use c99 SunOS  program c      SHELL VARIABLE  -D SOLARIS STUFF HERE       rm -f program     c99   SHELL VARIABLE  -o program program c

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Detect the operating system using two simple tricks    First the environment variable OS Then the uname command     ifeq    OS  Windows NT        is Windows NT on XP  2000  7  Vista  10        detected OS    Windows else     detected OS      shell uname     same as  uname -s  endif   Or a more safe way  if not on Windows and uname unavailable   ifeq    OS  Windows NT       detected OS    Windows else     detected OS      shell sh -c  uname 2 gt  dev null    echo Unknown   endif   Ken Jackson proposes an interesting alternative if you want to distinguish Cygwin MinGW MSYS Windows  See his answer that looks like that   ifeq    findstring     PATH            detected OS    Windows else     detected OS      shell uname 2 gt  dev null    echo Unknown      detected OS      patsubst CYGWIN  Cygwin   detected OS       detected OS      patsubst MSYS  MSYS   detected OS       detected OS      patsubst MINGW  MSYS   detected OS   endif   Then you can select the relevant stuff depending on detected OS   ifeq    detected OS  Windows      CFLAGS    -D WIN32 endif ifeq    detected OS  Darwin           Mac OS X     CFLAGS    -D OSX endif ifeq    detected OS  Linux      CFLAGS        -D LINUX endif ifeq    detected OS  GNU              Debian GNU Hurd     CFLAGS        -D GNU HURD endif ifeq    detected OS  GNU kFreeBSD     Debian kFreeBSD     CFLAGS        -D GNU kFreeBSD endif ifeq    detected OS  FreeBSD      CFLAGS        -D FreeBSD endif ifeq    detected OS  NetBSD      CFLAGS        -D NetBSD endif ifeq    detected OS  DragonFly      CFLAGS        -D DragonFly endif ifeq    detected OS  Haiku      CFLAGS        -D Haiku endif   Notes    Command uname is same as uname -s because option -s  --kernel-name  is the default  See why uname -s is better than uname -o  The use of OS  instead of uname  simplifies the identification algorithm  You can still use solely uname  but you have to deal with if else blocks to check all MinGW  Cygwin  etc  variations  The environment variable OS is always set to  Windows NT  on different Windows versions  see  OS  environment variable on Wikipedia   An alternative of OS is the environment variable MSVC  it checks the presence of MS Visual Studio  see example using Visual C         Below I provide a complete example using make and gcc to build a shared library    so or   dll depending on the platform  The example is as simplest as possible to be more understandable   To install make and gcc on Windows see Cygwin or MinGW   My example is based on five files    -- lib        -- Makefile        -- hello h        -- hello c   -- app       -- Makefile       -- main c   Reminder  Makefile is indented using tabulation  Caution when copy-pasting below sample files   The two Makefile files  1  lib Makefile  ifeq    OS  Windows NT      uname S    Windows else     uname S      shell uname -s  endif  ifeq    uname S   Windows      target   hello dll endif ifeq    uname S   Linux      target   libhello so endif  ifeq    uname S           See https   stackoverflow com a 27776822 938111      target          endif    o    c     gcc  -c   lt   -fPIC  -o          -c   lt     gt    lt  is first file after       gt  Compile hello c       -fPIC    gt  Position-Independent Code  required for shared lib        -o       gt     is the target   gt  Output file  -o  is hello o    target   hello o     gcc      -shared  -o                    gt     expand to all prerequisites  after        gt  hello o       -shared   gt  Generate shared library       -o        gt  Output file  -o  is     libhello so or hello dll    2  app Makefile  ifeq    OS  Windows NT      uname S    Windows else     uname S      shell uname -s  endif  ifeq    uname S   Windows      target   app exe endif ifeq    uname S   Linux      target   app endif  ifeq    uname S           See https   stackoverflow com a 27776822 938111      target          endif    o    c     gcc  -c   lt  -I    lib  -o          -c   lt        gt  compile  -c    lt   first file after      main c       -I    lib   gt  search headers    h  in directory    lib       -o          gt  output file  -o  is     target    main o    target   main o     gcc      -L   lib  -lhello  -o                     gt      all files after the      main o  here only one file        -L   lib   gt  look for libraries in directory    lib       -lhello    gt  use shared library hello  libhello so or hello dll        -o         gt  output file  -o  is     target     app exe  or  app    To learn more  read Automatic Variables documentation as pointed out by cfi   The source code  - lib hello h   ifndef HELLO H   define HELLO H   const char  hello      endif   - lib hello c   include  hello h   const char  hello         return  hello       - app main c   include  hello h    hello    include  lt stdio h gt    puts    int main         const char  str   hello        puts str       The build  Fix the copy-paste of Makefile  replace leading spaces by one tabulation     gt  sed   s       t    -i    Makefile   The make command is the same on both platforms  The given output is on Unix-like OSes    gt  make -C lib make  Entering directory   tmp lib  gcc  -c hello c  -fPIC  -o hello o   -c hello c    gt  hello c is first file after       gt  Compile hello c   -fPIC         gt  Position-Independent Code  required for shared lib    -o hello o    gt  hello o is the target   gt  Output file  -o  is hello o gcc  hello o  -shared  -o libhello so   hello o          gt  hello o is the first after       gt  Link hello o   -shared          gt  Generate shared library   -o libhello so   gt  Output file  -o  is libhello so  libhello so or hello dll  make  Leaving directory   tmp lib    gt  make -C app make  Entering directory   tmp app  gcc  -c main c -I    lib  -o main o   -c main c   gt  compile  -c  main c  first file after      main cpp   -I    lib   gt  search headers    h  in directory    lib   -o main o   gt  output file  -o  is main o  target    main o gcc  main o  -L   lib  -lhello  -o app   main o     gt  main o  all files after the      main o  here only one file    -L   lib   gt  look for libraries in directory    lib   -lhello    gt  use shared library hello  libhello so or hello dll    -o app     gt  output file  -o  is app exe  target     app exe  or  app  make  Leaving directory   tmp app    The run  The application requires to know where is the shared library   On Windows  a simple solution is to copy the library where the application is    gt  cp -v lib hello dll app  lib hello dll  - gt   app hello dll    On Unix-like OSes  you can use the LD LIBRARY PATH environment variable    gt  export LD LIBRARY PATH lib   Run the command on Windows    gt  app app exe hello   Run the command on Unix-like OSes    gt  app app hello

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Update  I now consider this answer to be obsolete   I posted a new perfect solution further down   If your makefile may be running on non-Cygwin Windows  uname may not be available  That s awkward  but this is a potential solution  You have to check for Cygwin first to rule it out  because it has WINDOWS in its PATH environment variable too   ifneq     findstring  cygdrive    PATH        UNAME    Cygwin else ifneq     findstring WINDOWS   PATH        UNAME    Windows else     UNAME      shell uname -s  endif endif

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I finally found the perfect solution that solves this problem for me   ifeq    findstring     PATH            UNAME    Windows else     UNAME      shell uname 2 gt  dev null    echo Unknown      UNAME      patsubst CYGWIN  Cygwin   UNAME       UNAME      patsubst MSYS  MSYS   UNAME       UNAME      patsubst MINGW  MSYS   UNAME   endif   The UNAME variable is set to Linux  Cygwin  MSYS  Windows  FreeBSD  NetBSD  or presumably Solaris  Darwin  OpenBSD  AIX  HP-UX   or Unknown   It can then be compared throughout the remainder of the Makefile to separate any OS-sensitive variables and commands   The key is that Windows uses semicolons to separate paths in the PATH variable whereas everyone else uses colons    It s possible to make a Linux directory with a     in the name and add it to PATH  which would break this  but who would do such a thing    This seems to be the least risky method to detect native Windows because it doesn t need a shell call   The Cygwin and MSYS PATH use colons so uname is called for them   Note that the OS environment variable can be used to detect Windows  but not to distinguish between Cygwin and native Windows   Testing for the echoing of quotes works  but it requires a shell call   Unfortunately  Cygwin adds some version information to the output of uname  so I added the  patsubst  calls to change it to just  Cygwin    Also  uname for MSYS actually has three possible outputs starting with MSYS or MINGW  but I use also patsubst to transform all to just  MSYS    If it s important to distinguish between native Windows systems with and without some uname exe on the path  this line can be used instead of the simple assignment   UNAME      shell uname 2 gt NUL    echo Windows    Of course in all cases GNU make is required  or another make which supports the functions used

[makefile] OS detecting makefile

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