如何把数据保存成16进制写入文件

#include 
#include 

int main(int argc,char *argv[])
{
	char *strTest = "hello world";
	int strLen=strlen(strTest);
	int i=0;
	FILE *fp;
	if((fp=fopen("text.txt", "wb")) == NULL)
	{
		printf("file open failed!");
		return 0;
	}
	printf("%d\n",strLen);
	while(i