c++

gistfile1.cpp

#define _XOPEN_SOURCE 500
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int main(){
        char* ds=new char[10];
        for(unsigned int i = 0 ; i<10;i++)
                ds[i]=65;
        int fd = open("./f",O_WRONLY , 666);
        int ssize = pwrite(fd, ds, 10,10);
}

nodejs

var fs = require('fs')

var b = Buffer('AAAAAAAAAA');

fs.open('./f','w', '666' , function(err, fd){
        fs.write(fd,b,0,10,10)
});