How to detect Operating System through a C program

One can find out the operating system on which the program is running with the help of C programming. This piece of information is very useful for the case where we want to build platform independent program. To find the OS (Operating System) we check out the macro defined by the compiler, for example windows with 32-bit OS has “_WIN32” as macro so if the macro is defined then the system we are working on is windows with 32-bit operating system. Similarly other OS has different macro defined. The list of macro for some popular OS are as follows:

Sr. No.	Operating System	Macro Present	Notes
1.	Windows 32-bit + 64-bit	_WIN32	for all Windows OS
2.	Windows 64 bit	_WIN64	Only for 64 bit windows
3.	Apple	__APPLE__	For all Apple OS
4.	Apple	__MACH__	alternative to above
5.	iOS embedded	TARGET_OS_EMBEDDED	include TargetConditionals.h
6.	iOS simulator	TARGET_IPHONE_SIMULATOR	include TargetConditionals.h
7.	iPhone	TARGET_OS_IPHONE	include TargetConditionals.h
8.	MacOS	TARGET_OS_MAC	include TargetConditionals.h
9.	Android	__ANDROID__	subset of linux
10.	Unix based OS	__unix__	–
11.	Linux	__linux__	subset of unix
12.	POSIX based	_POSIX_VERSION	Windows with Cygwin
13.	Solaris	__sun	–
14.	HP UX	__hpux	–
15.	BSD	BSD	all BSD flavors
16.	DragonFly BSD	__DragonFly__	–
17.	FreeBSD	__FreeBSD__	–
18.	NetBSD	__NetBSD__	–
19.	OpenBSD	__OpenBSD__	–

Note:

It must be noted that the macros are valid for GNU GCC and G++ and may vary for other compilers.

Below is the program to detect which OS we are working on:

C

// C program to detect Operating System

#include <stdio.h>

// Driver Code
int main()
{

// Checking for windows OS with
// _WIN32 macro
#ifdef _WIN32
    printf("Hey Geek it seems that"
           "you are working on a Windows OS.\n");

// Checking for mac OS with
// __APPLE__ macro
#elif __APPLE__
    printf("Hey Geek it seems that you"
           "are working on a Mac OS.\n");

// Checking for linux OS with
// __linux__ macro
#elif __linux__
    printf("Hey Geek it seems that you"
           "are working on a Linux OS.\n");

// Checking for iOS embedded OS with
// TARGET_OS_EMBEDDED macro
#elif TARGET_OS_EMBEDDED
    printf("Hey Geek it seems that you"
           "are working on an iOS embedded OS.\n");

// Checking for iOS simulator OS with
// TARGET_IPHONE_SIMULATOR macro
#elif TARGET_IPHONE_SIMULATOR
    printf("Hey Geek it seems that you"
           "are working on an iOS simulator OS.\n");

// Checking for iPhone OS with
// TARGET_OS_IPHONE macro
#elif TARGET_OS_IPHONE
    printf("Hey Geek it seems that you"
           "are working on an iPhone OS.\n");

// Checking for MAC OS with
// TARGET_OS_MAC macro
#elif TARGET_OS_MAC
    printf("Hey Geek it seems that you"
           "are working on a MAC OS.\n");

// Checking for Android OS with
// __ANDROID__ macro
#elif__ANDROID__
    printf("Hey Geek it seems that you"
           "are working on an android OS.\n");

// Checking for unix OS with
// __unix__ macro
#elif __unix__
    printf("Hey Geek it seems that you"
           "are working on a unix OS.\n");

// Checking for POSIX based OS with
// _POSIX_VERSION macro
#elif _POSIX_VERSION
    printf("Hey Geek it seems that you"
           "are working on a POSIX based OS.\n");

// Checking for Solaris OS with
// __sun macro
#elif __sun
    printf("Hey Geek it seems that you"
           "are working on a Solaris OS.\n");

// Checking for HP UX OS with
// __hpux macro
#elif __hpux
    printf("Hey Geek it seems that you"
           "are working on a HP UX OS.\n");

// Checking for BSD OS with
// BSD macro
#elif BSD
    printf("Hey Geek it seems that you"
           "are working on a Solaris OS.\n");

// Checking for DragonFly BSD OS with
// __DragonFly__ macro
#elif __DragonFly__
    printf("Hey Geek it seems that you"
           "are working on a DragonFly BSD OS.\n");

// Checking for FreeBSD OS with
// __FreeBSD__ macro
#elif __FreeBSD__
    printf("Hey Geek it seems that you"
           "are working on a FreeBSD OS.\n");

// Checking for Net BSD OS with
// __NetBSD__ macro
#elif __NetBSD__
    printf("Hey Geek it seems that you"
           "are working on a Net BSD OS.\n");

// Checking for Open BSD OS with
// __OpenBSD__ macro
#elif __OpenBSD__
    printf("Hey Geek it seems that you"
           "are working on an Open BSD OS.\n");

// If neither of them is present
// then this is printed...
#else
    printf("Sorry, the system are"
           "not listed above.\n");
#endif
    return 0;
}

Output:
Below is the output of the above program on a Windows OS:

Similarly one can find out the operating system and can set the appropriate code for the system