在前面的基础上，加上了修改功能和排序功能，可以选择姓名排序，年龄排序，价格排序。

test.c源文件

#include "Pet.h"

void menu()
{
	printf("------------------------\n");
	printf("-   欢迎来到宠物商店   -\n");
	printf("-              1.add   -\n");
	printf("-             2.show   -\n");
	printf("-             3.del    -\n");
	printf("-           4.modify   -\n");
	printf("-           5.sort     -\n");
	printf("-   欢迎来到宠物商店   -\n");
	printf("------------------------\n");

}

int main()
{
	printf("hello world\n");
	init(&shop);
	load(&shop);
	int input = 0;
	do
	{
		menu();
		scanf("%d", &input);
		switch (input)
		{
		case 1:
			add(&shop);
			break;
		case 2:
			show(&shop);
			break;
		case 3:
			del(&shop);
			break;
		case 4:
			modify(&shop);
			break;
		case 5:
			sort(&shop);
			break;
		case 0:
			Save(&shop);
			Destroy(&shop);
			printf("退出程序\n");
			break;
		default:
			printf("你的输入不对，请重新输入\n");
			break;
		}
	} while (input);
	return 0;
}

Pet.c源文件

#include "Pet.h"

int ssearch(struct Shop* pc, char* name);

void init(struct Shop* pc)
{
	pc->data= (struct Pet*)malloc(init_value * (sizeof(struct Pet)));
	if (pc->data == NULL)
	{
		perror("malloc");
		return;
	}
	pc->sz = 0;
	pc->capcity = init_value;
}

int check(struct Shop* pc)
{
	if (pc->sz == pc->capcity)
	{
		struct Pet* ptr = realloc(pc->data, (init_value + cre_value) * sizeof(struct Pet));
		if (ptr == NULL)
		{
			perror("realloc");
			return 0;
		}
		pc->data = ptr;
		pc->capcity += cre_value;
		printf("增容成功\n");
		return 1;
	}
	return 1;
}

void add(struct Shop* pc)
{
	int ret = check(pc);
	if (ret == 0)
	{
		return;
	}

	printf("请输入名字:>\n");
	char name[20];
	scanf("%s", name);
	//scanf("%s", pc->data[pc->sz].name);	
	int pos = ssearch(pc, name);
	if (pos != -1)
	{
		printf("该宠物名字已存在，不能重名\n");
		return;
	}
	strcpy(pc->data[pc->sz].name, name);
	printf("请输入年龄:>\n");
	scanf("%d", &(pc->data[pc->sz].age));
	printf("请输入价格:>\n");
	scanf("%f", &(pc->data[pc->sz].price));
	printf("请输入性别:>\n");
	scanf("%s", pc->data[pc->sz].sex);
	printf("增加宠物成功\n");
	pc->sz++;
}

void show(struct Shop* pc)
{
	int i = 0;
	printf("%-10s %-10s %-10s %-10s", "姓名", "年龄", "价格", "性别");
	printf("\n");
	for (i = 0; i < pc->sz; i++)
	{
		printf("%-10s %-10d %-10.2f %-10s\n", pc->data[i].name,pc->data[i].age,pc->data[i].price,pc->data[i].sex);
	}
}


void Save(struct Shop* pc)
{
	FILE* pf = fopen("test.txt", "wb");
	if (pf == NULL)
	{
		perror("Save");
		return;
	}
	int i = 0;
	for (i = 0; i < pc->sz; i++)
	{
		fwrite(pc->data+i, sizeof(struct Pet), 1, pf);//
	}
	//free(pf);  写错了，怪不得加上这个，文件里啥都没有 ,err
	fclose(pf);
	pf = NULL;
}


void Destroy(struct Shop* pc)
{
	free(pc->data);
	pc->data = NULL;
	pc->capcity = 0;
	pc->sz = 0;
}


void load(struct Shop* pc)
{
	FILE* pf = fopen("test.txt", "rb");
	if (pf == NULL)
	{
		perror("load");
		return;
	}
	struct Pet tmp = {0};
	while (fread(&tmp, sizeof(struct Pet), 1, pf)>=1)
	{
		if (check(pc) == 0)
		{
			return;
		}
		pc->data[pc->sz] = tmp;
		pc->sz++;
	}
	if (feof(pf))
	{
		printf("end of file reach successfully\n");
	}
	else if (ferror(pf))
	{
		printf("i/o error when read\n");
	}
	fclose(pf);
	pf = NULL;
}

int ssearch(struct Shop* pc,char* name)
{
	int i = 0;
	for (i = 0; i < pc->sz; i++)
	{
		if (strcmp(name, pc->data[i].name) == 0)
		{
			return i;
		}
	}
	return -1;
}

void del(struct Shop* pc)
{
	if (pc->sz == 0)
	{
		printf("没有宠物可删除\n");
		return;
	}
	printf("请输入要删除的名字:>\n");
	char name[20];
	scanf("%s", name);
	int ret = ssearch(pc,name);

	if (ret == -1)
	{
		printf("没找到\n");
		return;
	}
		printf("找到了，是%s %d %f %s", pc->data[ret].name, pc->data[ret].age, pc->data[ret].price, pc->data[ret].sex);
		printf("\n");
		int i = 0;
		for (i = ret; i < pc->sz-1; i++)//i等于ret，小于最后一个下标
		{
			//pc->data[ret] = pc->data[ret + 1]; err
			//pc->data[i] = pc->data[i + 1];第一种方法
			memmove(&(pc->data[i]), &(pc->data[i + 1]), sizeof(struct Pet));//目的地，源头，要复制的字节数
		}	
		printf("删除成功\n");
		pc->sz--;
}

void modify(struct Shop* pc)
{
	printf("请输入你要查找修改的名字:>\n");
	char name[20];
	scanf("%s", name);
	int m = ssearch(pc, name);
	if (m == -1)
	{
		printf("没找到要修改的名字\n");
		return;
	}
	printf("找到了，是%s %d %f %s", pc->data[m].name, pc->data[m].age, pc->data[m].price, pc->data[m].sex);
	printf("\n");
	printf("请输入修改后的名字:>\n");
	scanf("%s", name);
	int m1 = ssearch(pc, name);
	if (m1 != -1)
	{
		printf("该宠物名字已存在，不能重名\n");
		return;
	}
	strcpy(pc->data[m].name, name);
	printf("请输入修改后的年龄:>\n");
	scanf("%d", &(pc->data[m].age));
	printf("请输入修改后的价格:>\n");
	scanf("%f", &(pc->data[m].price));
	printf("请输入修改后的性别:>\n");
	scanf("%s", pc->data[m].sex);
}


int cmp1(const void* p1, const void* p2)//按姓名
{
	return strcmp(((struct Pet*)p1)->name, ((struct Pet*)p2)->name);
}
int cmp2(const void* p1, const void* p2)//按年龄
{
	return ((struct Pet*)p1)->age - ((struct Pet*)p2)->age;
}
int cmp3(const void* p1, const void* p2)//按价格
{
	if (((struct Pet*)p1)->price - ((struct Pet*)p2)->price > 0)
		return 1;
	if (((struct Pet*)p1)->price - ((struct Pet*)p2)->price < 0)
		return -1;
	return 0;
}

void sort(struct Shop* pc)
{
	int sort1 = 0;
	do
	{
		printf("按姓名排序:>1\n");
		printf("按年龄排序:>2\n");
		printf("按价格排序:>3\n");
		printf("退出:>0\n");
		scanf("%d", &sort1);
		if (sort1 == 1)
			qsort(pc->data, pc->sz, sizeof(struct Pet), cmp1);
		if (sort1 == 2)
			qsort(pc->data, pc->sz, sizeof(struct Pet), cmp2);
		if (sort1 == 3)
			qsort(pc->data, pc->sz, sizeof(struct Pet), cmp3);
		if(sort1!=3&&sort1!=2&&sort1!=1&&sort1!=0)
			printf("选择不对，请重新选择\n");
	} while (sort1);

}

Pet.h头文件 

#pragma once
#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define init_value 3
#define cre_value 2
#define NAME 20
#define SEX 5

struct Pet
{
	char name[NAME];
	int age;
	float price;
	char sex[SEX];
};

struct Shop
{
	struct Pet* data;
	int sz;
	int capcity;
};

struct Shop shop;

void init(struct Shop* pc);

void add(struct Shop*pc);

void show(struct Shop* pc);

void Save(struct Shop* pc);

void Destroy(struct Shop* pc);

void load(struct Shop* pc);

void del(struct Shop* pc);

void modify(struct Shop* pc);

void sort(struct Shop* pc);