2、在第一题的基础上，将这些数据按照学号升序进行排序，排序结果写入“stud_info2.csv”文件中，用excel开启表格文件，观察结果是否正确。

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
#define N 100

struct student{
	int num;
	char name[20];
};

void swap_student(struct student *a, struct student *b)
{
	struct student tmp;
	tmp=*a;
	*a=*b;
	*b=tmp;
}

void sort_soap(struct student list[],int len)
{
	int i, j;
	for(j=0;j<len-1;j++){
		for(i=0;i<len-j-1;i++){
			if(list[i].num>list[i+1].num){
				swap_student(&list[i],&list[i+1]);
		}
	}
}
}
void main(void)
{
	int i;
	struct student list[N]={0};
	int ret;
	int n;

	FILE *infp,*outfp;
	char ch;
	
	if((infp=fopen("stud_info.csv","r"))==NULL){
		printf("Cannot open infile.c.\n");
		exit(0);
	}
	
	for(i=0;i<N;i++){
		ret=fscanf(infp, "%d,%s",&list[i].num, &list[i].name);
		if (ret<2)
			break;
	}
	n=i;
	sort_soap(list, n);
	if((outfp=fopen("stud_info2.csv","w"))==NULL){
		printf("Cannot open outfile.c.\n");
		exit(0);
	}
	
	for(i=0;i<n;++i){
		fprintf(outfp, "%d, %s\n",list[i].num, list[i].name);
		
	}
	fclose(infp);
	fclose(outfp);
}