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>#endifint main(int argc, char *argv[]) {#ifdef _WIN32MEMORYSTATUSEX statex; statex.dwLength = sizeof (statex); GlobalMemoryStatusEx (&statex); _tprintf (TEXT("There is %*ld %% of memory in use.n"), WIDTH, statex.dwMemoryLoad);#endif#ifdef linuxchar cmd[30];int flag = 0; FILE *fp;char line[130]; int TotalMem, TotalFree, TotalUsed;flag=0;memcpy (cmd," ",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:%dn",TotalMem,TotalUsed,TotalFree);else printf("not foundn");#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。
