在C，C ++中检测Windows或Linux

Question

我正在编写一个跨平台程序。我希望这个程序可以在Windows和Linux上运行，所以对于两个平台，我有两个不同的代码段。如果操作系统是Windows，则我希望第一个代码段可以运行；如果是Linux，那么我要运行第二个代码段。

所以我写了下面的代码，但是在Windows和Linux上构建时都会出错。我该怎么解决？

#ifdef __unix__                    /* __unix__ is usually defined by compilers targeting Unix systems */

    #define OS_Windows 0
    #include <unistd.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>

#elif defined(_WIN32) || defined(WIN32)     /* _Win32 is usually defined by compilers targeting 32 or   64 bit Windows systems */

    #define OS_Windows 1
    #include <windows.h>
    #include <stdio.h>
    #include <tchar.h>
    #define DIV 1048576
    #define WIDTH 7

#endif

int main(int argc, char *argv[])
{
    if(OS_Windows)
    {
        MEMORYSTATUSEX statex;
        statex.dwLength = sizeof (statex);
        GlobalMemoryStatusEx (&statex);

        _tprintf (TEXT("There is  %*ld %% of memory in use.\n"),
                    WIDTH, statex.dwMemoryLoad);

    }

    else if(!OS_Windows) // if OS is unix

    {
        char cmd[30];
        int flag = 0;
        FILE *fp;
        char line[130];
        int memTotal, memFree, memUsed;

        flag=0;
        memcpy (cmd,"\0",30);
        sprintf(cmd,"free -t -m|grep Total");
        fp = popen(cmd, "r");
        while ( fgets( line, sizeof line, fp))
        {
            flag++;
            sscanf(line,"%*s %d %d %d",&TotalMem, &TotalUsed, &TotalFree);
        }
        pclose(fp);

        if(flag)
            printf("TotalMem:%d -- TotalUsed:%d -- TotalFree:%d\n",TotalMem,TotalUsed,TotalFree);
        else
            printf("not found\n");

    }

    return 0;
}

Answer 1

通常是这样完成的（或多或少）：

#ifdef _WIN32
#include <windows.h>
#include <stdio.h>
#include <tchar.h>

#define DIV 1048576 
#define WIDTH 7
#endif

#ifdef linux
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#endif


int main(int argc, char *argv[]) 
{
#ifdef _WIN32
MEMORYSTATUSEX statex;
    statex.dwLength = sizeof (statex);
    GlobalMemoryStatusEx (&statex);

    _tprintf (TEXT("There is  %*ld %% of memory in use.\n"),
            WIDTH, statex.dwMemoryLoad);
#endif

#ifdef linux
char cmd[30];
int flag = 0;   
FILE *fp;
char line[130];     
int TotalMem, TotalFree, TotalUsed;

flag=0;
memcpy (cmd,"\0",30);
sprintf(cmd,"free -t -m|grep Total");          
fp = popen(cmd, "r");       
while ( fgets( line, sizeof line, fp))
{   
    flag++;
    sscanf(line,"%*s %d %d %d",&TotalMem, &TotalUsed, &TotalFree);
}
pclose(fp);

if(flag)
    printf("TotalMem:%d -- TotalUsed:%d -- TotalFree:%d\n",TotalMem,TotalUsed,TotalFree);
else 
    printf("not found\n");
#endif

    return 0;
}

这样，只有在Linux平台上才编译linux的代码，而只有Windows平台上才编译Windows的代码。