linux下c语言大内存分配

 #include<stdio.h>
#include<string.h>
#include<malloc.h>
#include<sys/mman.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>

int main(int argc,char**argv)
{
    char *x=NULL;
    int fd;

    if((fd=open(argv[1],O_RDWR))==-1)
    {
        printf("failed to open\n");
    }

    x=mmap(0,3001*3001*1200*sizeof(char),PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);

    if(x==NULL)
        printf("failed\n");
    else 
        printf("x=0x%x\n",x);

     return 0;
}