C language implementation of classroom random roll call system

Today, review the curriculum design written in school , Review what you learned in school , At the same time, I also hope to help those poor people who are tortured by the curriculum like me ~

1、 Project requirement

Random roll call procedure in class
requirement It can fully realize the existing functions of our roll call program . That is, download the list of students in a class from the website of the academic affairs office and save it for future use . Your program can selectively load the save file of a class in some way and read the corresponding student information into memory , And then to Random To find the information of a student and display it to realize roll call .

2、 Implementation of project functions

To achieve a complete roll call system , except The most basic random roll call , There needs to be more 、 Delete 、 modify And so on , This requires us to think , Implement them in a functional way . following , Is the function I used in this project .

First, let's take a look at the software structure diagram of the project

First, define a structure , Because it is only used for class roll call , Therefore, the information of students in the structure here only includes student number and name .

typedef struct StuInfo
{
    
	int id;
    char name[MAX];
}StuInfo;

Function one ： Read the contents of the selected open file into the structure

// Read the contents of the file into the structure 
void stu_open(char* file, FILE* fp,StuInfo* s,int num)
{
    
	int i = 0;
	fscanf(fp, "%d", &num);// Number of students enrolled in class 
	for (i = 0; i < num; i++)
	{
    
		fscanf(fp, "%d %s", &(s[i].id), s[i].name);// Read the information of each student in a circle 
	}
	return;
}

When passing parameters here ,file Is to select the file to open ,s Structure array created for ,num For class size , These will be presented later in the complete code , Because here is to explain the specific code content , Therefore, the specific creation process is not reflected . The transmission of the following functions is the same .

Function two ： Random roll call function

// Random roll call 
void stu_byname(char* file,StuInfo* s,int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	int i = 0;
	i = rand() % num;// Get the random number in the class number 
	printf("\n Student number : %d\n full name : %s\n", s[i].id, s[i].name);// Print and display the student information corresponding to the random number 
}

The random number generator has been set in the main function ：srand((unsigned int)time(NULL)), Therefore, we only need to use it directly rand() Get a random number .

By the way, let's explain how random numbers are obtained ：
srand Set a random number seed for , To prevent the repetition of random numbers generated each time , Therefore, we need to set different random number seeds , And time is changing every moment , So we can use timestamp as random number seed , To generate different random numbers .time Function can generate the timestamp of the current time , Its standard form is time_t time (time_t* timer), Its parameter is a pointer , We just need to call time function , Therefore, the parameter can be written directly as NULL,time The return type of is time_t, and srand What you need is an integer , So we also need to cast it to unsigned int , This constitutes our final random number generator ：srand((unsigned int)time(NULL)), When generating random numbers later , Just call rand() Function .

Time stamp ：

Function three ： Add student information

// Add student information 
void stu_add(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	int i = 0;
	int j = 0;
	int m = 0;
	char str[20] = {
     0 };
	printf(" Please enter the student number and name of the added student :>");
	scanf("%d %s", &m, &str);

	// Judge whether the student number already exists 
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			printf(" The student number already exists !\n");
			printf(" Add failure !\n");
			break;
		}
	}

	// If it does not exist , Add to the student 
	if (i == num)
	{
    
		num = num + 1;
		// Reset the file pointer to the beginning of the file , And re write the class number 
		rewind(fp);
		fprintf(fp, "%d", num);
		// Move the file pointer to the end of the file , Write the newly added student 
		fseek(fp, 0, SEEK_END);
		fprintf(fp, "\n%d %s", m, str);
		printf(" Add success \n");
	}
}

Function four ： Delete student information

// Delete student information 
void stu_del(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	stu_close(file, fp);
	// Close the file , And start again with "w+" To open the file 
	FILE* ffp = fopen(file, "w+");
	int input = 0;
	int k = 0;
	do
	{
    
		menu_del();
		printf(" Please enter the deletion method :>");
		scanf("%d", &input);
		switch (input)
		{
    
		case 1:
			stu_del_id(file, fp,s,num);
			break;
		case 2:
			stu_del_name(file, fp,s,num);
			break;
	    // Because it is with "w+" The way to open the file , The contents will be emptied , therefore , If you cancel or exit delete , You need to write the contents of the structure into the file 
		case 0:
			fprintf(ffp, "%d\n", num);
			for (k = 0; k < num; k++)
			{
    
				fprintf(ffp, "%d %s", s[k].id, s[k].name);
				if (k < num - 1)
				{
    
					fputc('\n', ffp);
				}
			}
			printf(" Exit delete !\n");
			break;
		default:
			rewind(ffp);
			fprintf(ffp, "%d\n", num);
			for (k = 0; k < num; k++)
			{
    
				fprintf(ffp, "%d %s", s[k].id, s[k].name);
				if (k < num - 1)
				{
    
					fputc('\n', ffp);
				}
			}
			printf(" Input error ! Please re-enter !\n");
			break;
		}
		stu_close(file, ffp);
	} while (input);
}

Here is Two ways to delete ： Delete by student number and by name （ The following query 、 modify 、 Sorting also includes these two methods ）, And confirm the deletion and other operations , Further improve the function of the code . Next is the specific code of the two deletion methods ：

// Delete by student number 
void stu_del_id(char* file, FILE* fp,StuInfo* s,int num)
{
    
	int m = 0;
	int i = 0;
	int j = 0;
	int k = 0;
	int flag = 0;
	
	printf(" Please enter the student number to delete :>");
	scanf("%d", &m);
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			// Confirm whether to delete 
			printf(" The student information is :\n");
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			printf(" Are you sure you want to delete this student's information ?(0/1):>");
			scanf("%d", &flag);
			switch (flag)
			{
    
			case 1:
				for (j = i; j < num; j++)
				{
    
					s[j] = s[j + 1];
				}
				num--;
				// Reset the file pointer to the beginning of the file , And re write the class number 
				rewind(fp);
				fprintf(fp, "%d\n", num);
				for (k = 0; k < num; k++)
				{
    
					fprintf(fp, "%d %s", s[k].id, s[k].name);
					if (k < num - 1)
					{
    
						fputc('\n', fp);
					}
				}
				printf(" Delete successful !\n");
				break;
			case 0:
				printf(" Successful operation ! Cancel deletion , Go back to the upper menu !\n");
				break;
			default:
				printf(" Input error ! Please re-enter :>\n");
				break;
			}
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The student number does not exist !\n");
		printf(" Delete failed !\n");
	}
}

// Delete by name 
void stu_del_name(char* file, FILE* fp,StuInfo* s,int num)
{
    
	int i = 0;
	int j = 0;
	int k = 0;
	int flag = 0;
	char str[20] = {
     0 };
	//fscanf(fp, "%d\n", &num);
	//stu_open(file, fp, s, num);
	printf(" Please enter the name to delete :>");
	scanf("%s", &str);
	for (i = 0; i < num; i++)
	{
    
		if (strcmp(s[i].name, str) == 0)
		{
    
			// Confirm whether to delete 
			printf(" The student information is :\n");
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			printf(" Are you sure you want to delete this student's information ?(0/1):>");
			scanf("%d", &flag);
			switch (flag)
			{
    
			case 1:
				for (j = i; j < num; j++)
				{
    
					s[j] = s[j + 1];
				}
				num--;
				// Reset the file pointer to the beginning of the file , And re write the class number 
				rewind(fp);
				fprintf(fp, "%d\n", num);
				for (k = 0; k < num; k++)
				{
    
					fprintf(fp, "%d %s", s[k].id, s[k].name);
					if (k < num - 1)
					{
    
						fputc('\n', fp);
					}
				}
				printf(" Delete successful !\n");
				break;
			case 0:
				printf(" Successful operation ! Cancel deletion , Go back to the upper menu !\n");
				break;
			default:
				printf(" Input error ! Please re-enter :>\n");
				break;
			}
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The name does not exist !\n");
		printf(" Delete failed !\n");
	}
}

The general idea of the two deletion methods is the same , It is to find the information of the student and print it first , Confirm whether to delete , After confirming the deletion , Cover up one by one with the information of the students behind , And reduce the number of classes by one , To achieve the effect of deleting information .

Function five ： Search for student information

// Query information 
void stu_located(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	int input = 0;
	do
	{
    
		menu_located();
		printf(" Please select the query method :>");
		scanf("%d", &input);
		switch (input)
		{
    
		case 1:
			located_id(s,num);
			break;
		case 2:
			located_name(s,num);
			break;
		case 0:
		    printf(" Cancel the query !\n");
			break;
		default:
			printf(" Input error ! Please re-enter :>\n");
			break;
		}
	} while (input);
}

// By student number 
void located_id(StuInfo* s, int num)
{
    
	int m = 0;
	int i = 0;
	printf(" Please enter the student number to inquire :>");
	scanf("%d", &m);
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			// The query is successful , Output the student information 
			printf(" The student information is :\n");
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The student number does not exist !\n");
	}
}

// Search by name 
void located_name(StuInfo* s, int num)
{
    

	char s1[MAX];
	int i = 0;
	int j = 0;

	printf(" Please enter the name you want to query :>");
	scanf("%s", &s1);
	for (i = 0; i < num; i++)
	{
    
		if (strcmp(s1, s[i].name) == 0)
		{
    
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The name does not exist !\n");
	}
}

Function six ： Modify student information

// Modify student information 
void stu_multify(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	int input = 0;
	do
	{
    
		menu_multify();
		printf(" Please select the modification method :>");
		scanf("%d", &input);
	switch (input)
		{
    
		case 1:
			multify_id(file, fp,s,num);
			break;
		case 2:
			multify_name(file, fp,s,num);
			break;
		case 0:
		    printf(" Cancel and modify !\n");
			break;
		default:
			printf(" Input error ! Please re-enter :>\n");
			break;
		}
	} while (input);
}

// Enter student number to modify 
void multify_id(char* file, FILE* fp, StuInfo* s, int num)
{
    
	char s1[20] = {
     0 };
	int i = 0;
	int j = 0;
	int k = 0;
	int m = 0;
	int n = 0;
	printf(" Please input the student number of the student to be modified :>");
	scanf("%d", &m);
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			printf(" The student number of the current student is :>%d  The name is :>%s\n", s[i].id, s[i].name);
			printf(" Please enter the modified student number :>");
			scanf("%d", &n);

			// Judge whether the modified student number already exists 
			for (k = 0; k < num; k++)
			{
    
				if (n == s[k].id)
				{
    
					printf(" The student number already exists !\n");
					printf(" The student's name is :>%s\n", s[k].name);
					break;
				}
			}
			if (k == num)
			{
    
				s[i].id = n;
				printf(" The student's student number after revision is :>%d  The name is :>%s\n", s[i].id, s[i].name);
				rewind(fp);
				fprintf(fp, "%d\n", num);
				for (j = 0; j < num; j++)
				{
    
					fprintf(fp, "%d %s", s[j].id, s[j].name);
					if (j < num - 1)
					{
    
						fputc('\n', fp);
					}
				}
				printf(" Modification successful ！\n");
				break;
			}
		}
	}
	if (i > num)
	{
    
		printf(" The student number does not exist !\n");
		printf(" Modification failed !\n");
	}
}

// Enter the name to modify 
void multify_name(char* file, FILE* fp, StuInfo* s, int num)
{
    
	char s1[20] = {
     0 };
	char s2[20] = {
     0 };
	int i = 0;
	int j = 0;
	int k = 0;
	int m = 0;
	printf(" Please enter the name of the student to be modified :>");
	scanf("%s", &s1);
	for (i = 0; i < num; i++)
	{
    
		if (strcmp(s1, s[i].name) == 0)
		{
    
			printf(" The student number of the current student is :>%d  The name is :>%s\n", s[i].id, s[i].name);
			printf(" Please enter the modified name :>");
			scanf("%s", s1);
			strcpy(s[i].name, s1);
			printf(" The student's student number after revision is :>%d  The name is :>%s\n", s[i].id, s[i].name);
			rewind(fp);
			fprintf(fp, "%d\n", num);
			for (j = 0; j < num; j++)
			{
    
				fprintf(fp, "%d %s", s[j].id, s[j].name);
				if (j < num - 1)
				{
    
					fputc('\n', fp);
				}
			}
			printf(" Modification successful ！\n");
			break;
		}
	}
	if (i > num)
	{
    
		printf(" The name does not exist !\n");
		printf(" Modification failed !\n");
	}
}

Function seven ： Show student information

// Show student information 
void stu_show(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d\n", &num);
	int i = 0;
	printf(" The student information of this class is ：\n");
	printf(" Student number   full name \n");
	for (i = 0; i < num; i++)
	{
    
		printf("%d %s\n", s[i].id, s[i].name);
	}
}

Here, through the loop , Print and display the information of all students .

Function eight ： Sort student information

// Sort student information 
void stu_sort(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d\n", &num);
	int i = 0;
	int input = 0;
	menu_sort();
	printf(" Please select sort by :>");
	scanf("%d", &input);
	switch (input)
	{
    
	case 1:
		qsort(s, num, sizeof(s[0]), cmp_by_id);
		printf(" Sort complete !\n");
		break;
	case 2:
		qsort(s, num, sizeof(s[0]), cmp_by_name);
		printf(" Sort complete !\n");
		break;
	case 0:
		printf(" Unsort !\n");
		break;
	default:
		printf(" Input error ! Please re-enter :>\n");
		break;
	}

	rewind(fp);
	fprintf(fp, "%d\n", num);
	for (i = 0; i < num; i++)
	{
    
		fprintf(fp, "%d %s", s[i].id, s[i].name);
		if (i < num - 1)
		{
    
			fputc('\n', fp);
		}
	}
}

// Sort by student number 
int cmp_by_id(const void* e1, const void* e2)
{
    
	//e1、e2 by void* type , First convert its mandatory type to a structure (StuInfo*) type , Point to id Compare 
	return (((StuInfo*)e1)->id - ((StuInfo*)e2)->id);
}

// Sort by name 
int cmp_by_name(const void* e1, const void* e2)
{
    
	return strcmp(((StuInfo*)e1)->name, ((StuInfo*)e2)->name);
}

The sorting method I use here is qsort function ：

void qsort
(
void* base,// The first address of the array to be sorted
size_t num,// Number of elements of the array to be sorted
size_t width,// The size of each element of the array to be sorted （ In bytes ）
int (* cmp)(const void* e1,const void* e2)// A function pointer , The address of the function used to compare two elements （ This function should be implemented by itself ）, The two parameters are the addresses of the two elements to be compared
)

qsort There are four parameters inside the function , Here their meanings have been listed one by one . Note that when implementing the last function , The parameter type must be const void*.

3、 Project presentations

1. Exhibition

（ Because the functions are based on the existing class files , therefore , Here I first show the class student information .）

2. Roll call

3. Add

4. Delete

5. lookup

6. modify

7. Sort

4、 Code display

1. byname.h

（ Contains the definition of macros 、 The reference of header file, the declaration of function and the creation of structure ）
（ Don't forget to reference this header file in the next two files ）

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <errno.h>

#define MAX 100

// Create a structure 
typedef struct StuInfo
{
    
	int id;
	char name[MAX];
}StuInfo;

void stu_open(char* file, FILE* fp,StuInfo* s,int num);
void stu_byname(char* file,StuInfo* s,int num);
void stu_add(char* file,StuInfo* s,int num);
void stu_del(char* file,StuInfo* s,int num);
void stu_located(char* file,StuInfo* s,int num);
void stu_show(char* file,StuInfo* s,int num);
void stu_multify(char* file,StuInfo* s,int num);
void stu_sort(char* file,StuInfo* s,int num);
void stu_close(char* file, FILE* fp);

2. byname.c

（ Including the implementation of various functional functions ）

#define _CRT_SECURE_NO_WARNINGS 1

#include "byname.h"

// Read the contents of the file into the structure 
void stu_open(char* file, FILE* fp,StuInfo* s,int num)
{
    
	int i = 0;
	//stu_write(file, fp, count);
	fscanf(fp, "%d", &num);
	for (i = 0; i < num; i++)
	{
    
		fscanf(fp, "%d %s", &(s[i].id), s[i].name);
	}
	return;
}

// Random roll call 
void stu_byname(char* file,StuInfo* s,int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	//stu_open(file, fp, s, num);
	int i = 0;
	// Get a random number 
	i = rand() % num;
	printf("\n Student number : %d\n full name : %s\n", s[i].id, s[i].name);
}

// Add student information 
void stu_add(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	int i = 0;
	int j = 0;
	int m = 0;
	char str[20] = {
     0 };
	printf(" Please enter the student number and name of the added student :>");
	scanf("%d %s", &m, &str);

	// Judge whether the student number already exists 
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			printf(" The student number already exists !\n");
			printf(" Add failure !\n");
			break;
		}
	}

	// If it does not exist , Add to the student 
	if (i == num)
	{
    
		num = num + 1;
		// Reset the file pointer to the beginning of the file , And re write the class number 
		rewind(fp);
		fprintf(fp, "%d", num);
		// Move the file pointer to the end of the file , Write the newly added student 
		fseek(fp, 0, SEEK_END);
		fprintf(fp, "\n%d %s", m, str);
		printf(" Add success \n");
	}
}

// Delete menu 
void menu_del()
{
    
	printf("*********************************\n");
	printf("********* 1. Delete by student number  *********\n");
	printf("********* 2. Delete by name  *********\n");
	printf("********* 0. Cancel deletion  *********\n");
	printf("*********************************\n");
}

// Delete by student number 
void stu_del_id(char* file, FILE* fp,StuInfo* s,int num)
{
    
	int m = 0;
	int i = 0;
	int j = 0;
	int k = 0;
	int flag = 0;
	
	printf(" Please enter the student number to delete :>");
	scanf("%d", &m);
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			// Confirm whether to delete 
			printf(" The student information is :\n");
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			printf(" Are you sure you want to delete this student's information ?(0/1):>");
			scanf("%d", &flag);
			switch (flag)
			{
    
			case 1:
				for (j = i; j < num; j++)
				{
    
					s[j] = s[j + 1];
				}
				num--;
				// Reset the file pointer to the beginning of the file , And re write the class number 
				rewind(fp);
				fprintf(fp, "%d\n", num);
				for (k = 0; k < num; k++)
				{
    
					fprintf(fp, "%d %s", s[k].id, s[k].name);
					if (k < num - 1)
					{
    
						fputc('\n', fp);
					}
				}
				printf(" Delete successful !\n");
				break;
			case 0:
				printf(" Successful operation ! Cancel deletion , Go back to the upper menu !\n");
				break;
			default:
				printf(" Input error ! Please re-enter :>\n");
				break;
			}
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The student number does not exist !\n");
		printf(" Delete failed !\n");
	}

}

// Delete by name 
void stu_del_name(char* file, FILE* fp,StuInfo* s,int num)
{
    
	int i = 0;
	int j = 0;
	int k = 0;
	int flag = 0;
	char str[20] = {
     0 };
	//fscanf(fp, "%d\n", &num);
	//stu_open(file, fp, s, num);
	printf(" Please enter the name to delete :>");
	scanf("%s", &str);
	for (i = 0; i < num; i++)
	{
    
		if (strcmp(s[i].name, str) == 0)
		{
    
			// Confirm whether to delete 
			printf(" The student information is :\n");
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			printf(" Are you sure you want to delete this student's information ?(0/1):>");
			scanf("%d", &flag);
			switch (flag)
			{
    
			case 1:
				for (j = i; j < num; j++)
				{
    
					s[j] = s[j + 1];
				}
				num--;
				// Reset the file pointer to the beginning of the file , And re write the class number 
				rewind(fp);
				fprintf(fp, "%d\n", num);
				for (k = 0; k < num; k++)
				{
    
					fprintf(fp, "%d %s", s[k].id, s[k].name);
					if (k < num - 1)
					{
    
						fputc('\n', fp);
					}
				}
				printf(" Delete successful !\n");
				break;
			case 0:
				printf(" Successful operation ! Cancel deletion , Go back to the upper menu !\n");
				break;
			default:
				printf(" Input error ! Please re-enter :>\n");
				break;
			}
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The name does not exist !\n");
		printf(" Delete failed !\n");
	}
}

// Delete student information 
void stu_del(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	stu_close(file, fp);
	// Close the file , And start again with "w+" To open the file 
	FILE* ffp = fopen(file, "w+");
	int input = 0;
	int k = 0;
	do
	{
    
		menu_del();
		printf(" Please enter the deletion method :>");
		scanf("%d", &input);
		switch (input)
		{
    
		case 1:
			stu_del_id(file, fp,s,num);
			break;
		case 2:
			stu_del_name(file, fp,s,num);
			break;
	    // Because it is with "w+" The way to open the file , The contents will be emptied , therefore , If you cancel or exit delete , You need to write the contents of the structure into the file 
		case 0:
			fprintf(ffp, "%d\n", num);
			for (k = 0; k < num; k++)
			{
    
				fprintf(ffp, "%d %s", s[k].id, s[k].name);
				if (k < num - 1)
				{
    
					fputc('\n', ffp);
				}
			}
			printf(" Exit delete !\n");
			break;
		default:
			rewind(ffp);
			fprintf(ffp, "%d\n", num);
			for (k = 0; k < num; k++)
			{
    
				fprintf(ffp, "%d %s", s[k].id, s[k].name);
				if (k < num - 1)
				{
    
					fputc('\n', ffp);
				}
			}
			printf(" Input error ! Please re-enter !\n");
			break;
		}
		stu_close(file, ffp);
	} while (input);
}

// Query menu 
void menu_located()
{
    
	printf("--------------------------\n");
	printf("-------1. By student number -------\n");
	printf("-------2. Search by name -------\n");
	printf("-------0. Exit query ---------\n");
	printf("--------------------------\n");
}

// By student number 
void located_id(StuInfo* s, int num)
{
    
	int m = 0;
	int i = 0;
	printf(" Please enter the student number to inquire :>");
	scanf("%d", &m);
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			// The query is successful , Output the student information 
			printf(" The student information is :\n");
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The student number does not exist !\n");
	}
}

// Search by name 
void located_name(StuInfo* s, int num)
{
    

	char s1[MAX];
	int i = 0;
	int j = 0;

	printf(" Please enter the name you want to query :>");
	scanf("%s", &s1);
	for (i = 0; i < num; i++)
	{
    
		if (strcmp(s1, s[i].name) == 0)
		{
    
			printf(" Student number :>%d  full name :>%s\n", s[i].id, s[i].name);
			break;
		}
	}
	if (i == num)
	{
    
		printf(" The name does not exist !\n");
	}
}

// Query information 
void stu_located(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	int input = 0;
	do
	{
    
		menu_located();
		printf(" Please select the query method :>");
		scanf("%d", &input);
		switch (input)
		{
    
		case 1:
			located_id(s,num);
			break;
		case 2:
			located_name(s,num);
			break;
		case 0:
			break;
		default:
			printf(" Input error ! Please re-enter :>\n");
			break;
		}
	} while (input);
}

// Modify the menu 
void menu_multify()
{
    
	printf("*******************************\n");
	printf("********* 1. Change the student number  *********\n");
	printf("********* 2. Change the name  *********\n");
	printf("********* 0. Cancel and modify  *********\n");
	printf("*******************************\n");
}

// Enter student number to modify 
void multify_id(char* file, FILE* fp, StuInfo* s, int num)
{
    
	//fscanf(fp, "%d", &num);
	char s1[20] = {
     0 };
	int i = 0;
	int j = 0;
	int k = 0;
	int m = 0;
	int n = 0;
	printf(" Please input the student number of the student to be modified :>");
	scanf("%d", &m);
	for (i = 0; i < num; i++)
	{
    
		if (m == s[i].id)
		{
    
			printf(" The student number of the current student is :>%d  The name is :>%s\n", s[i].id, s[i].name);
			printf(" Please enter the modified student number :>");
			scanf("%d", &n);

			// Judge whether the modified student number already exists 
			for (k = 0; k < num; k++)
			{
    
				if (n == s[k].id)
				{
    
					printf(" The student number already exists !\n");
					printf(" The student's name is :>%s\n", s[k].name);
					break;
				}
			}
			if (k == num)
			{
    
				s[i].id = n;
				printf(" The student's student number after revision is :>%d  The name is :>%s\n", s[i].id, s[i].name);
				rewind(fp);
				fprintf(fp, "%d\n", num);
				for (j = 0; j < num; j++)
				{
    
					fprintf(fp, "%d %s", s[j].id, s[j].name);
					if (j < num - 1)
					{
    
						fputc('\n', fp);
					}
				}
				printf(" Modification successful ！\n");
				break;
			}
		}
	}
	if (i > num)
	{
    
		printf(" The student number does not exist !\n");
		printf(" Modification failed !\n");
	}
}

// Enter the name to modify 
void multify_name(char* file, FILE* fp, StuInfo* s, int num)
{
    
	//fscanf(fp, "%d", &num);
	char s1[20] = {
     0 };
	char s2[20] = {
     0 };
	int i = 0;
	int j = 0;
	int k = 0;
	int m = 0;
	printf(" Please enter the name of the student to be modified :>");
	scanf("%s", &s1);
	for (i = 0; i < num; i++)
	{
    
		if (strcmp(s1, s[i].name) == 0)
		{
    
			printf(" The student number of the current student is :>%d  The name is :>%s\n", s[i].id, s[i].name);
			printf(" Please enter the modified name :>");
			scanf("%s", s1);
			strcpy(s[i].name, s1);
			printf(" The student's student number after revision is :>%d  The name is :>%s\n", s[i].id, s[i].name);
			rewind(fp);
			fprintf(fp, "%d\n", num);
			for (j = 0; j < num; j++)
			{
    
				fprintf(fp, "%d %s", s[j].id, s[j].name);
				if (j < num - 1)
				{
    
					fputc('\n', fp);
				}
			}
			printf(" Modification successful ！\n");
			break;
		}
	}
	if (i > num)
	{
    
		printf(" The name does not exist !\n");
		printf(" Modification failed !\n");
	}
}

// Modify student information 
void stu_multify(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d", &num);
	int input = 0;
	do
	{
    
		menu_multify();
		printf(" Please select the modification method :>");
		scanf("%d", &input);
	switch (input)
		{
    
		case 1:
			multify_id(file, fp,s,num);
			break;
		case 2:
			multify_name(file, fp,s,num);
			break;
		case 0:
			break;
		default:
			printf(" Input error ! Please re-enter :>\n");
			break;
		}
	} while (input);

}

// Show student information 
void stu_show(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d\n", &num);
	int i = 0;
	printf(" The student information of this class is ：\n");
	printf(" Student number   full name \n");
	for (i = 0; i < num; i++)
	{
    
		printf("%d %s\n", s[i].id, s[i].name);
	}
}

// Sort menu 
void menu_sort()
{
    
	printf("***********************************\n");
	printf("********** 1. Sort by student number  ***********\n");
	printf("********** 2. Sort by name  ***********\n");
	printf("********** 0. Unsort  ***********\n");
	printf("***********************************\n");
}

qsort function 
//void qsort
// (
// void* base,// The first address of the array to be sorted 
// size_t num,// Number of elements of the array to be sorted 
// size_t width,// The size of each element of the array to be sorted （ In bytes ）
// int (*cmp)(const void* e1,const void* e2)// A function pointer , The address of the function used to compare two elements （ This function should be implemented by itself ）, Inside 
// ) // The two parameters of are the addresses of the two elements to be compared 

// Sort by student number 
int cmp_by_id(const void* e1, const void* e2)
{
    
	//e1、e2 by void* type , First convert its mandatory type to a structure (StuInfo*) type , Point to id Compare 
	return (((StuInfo*)e1)->id - ((StuInfo*)e2)->id);
}

// Sort by name 
int cmp_by_name(const void* e1, const void* e2)
{
    
	return strcmp(((StuInfo*)e1)->name, ((StuInfo*)e2)->name);
}

// Sort student information 
void stu_sort(char* file, StuInfo* s, int num)
{
    
	FILE* fp = fopen(file, "r+");
	fscanf(fp, "%d\n", &num);
	int i = 0;
	int input = 0;
	menu_sort();
	printf(" Please select sort by :>");
	scanf("%d", &input);
	switch (input)
	{
    
	case 1:
		qsort(s, num, sizeof(s[0]), cmp_by_id);
		break;
	case 2:
		qsort(s, num, sizeof(s[0]), cmp_by_name);
		break;
	case 0:
		printf(" Unsort !\n");
		break;
	default:
		printf(" Input error ! Please re-enter :>\n");
		break;
	}

	printf(" Sort complete !\n");
	rewind(fp);
	fprintf(fp, "%d\n", num);
	for (i = 0; i < num; i++)
	{
    
		fprintf(fp, "%d %s", s[i].id, s[i].name);
		if (i < num - 1)
		{
    
			fputc('\n', fp);
		}
	}
}

// Close file 
void stu_close(char* file, FILE* fp)
{
    
	fclose(fp);
	fp = NULL;
}

3.test.c

（ Contains the main function , And the codes of the first two documents ）

#define _CRT_SECURE_NO_WARNINGS 1
#include "byname.h"

void menu()
{
    
	printf("*****************************************************\n");
	printf("************* 1. Start roll call  2. Add  *************\n");
	printf("************* 3. Delete  4. lookup  *************\n");
	printf("************* 5. modify  6. Show  *************\n");
	printf("************* 7. Sort  0. sign out  *************\n");
	printf("*****************************************************\n");
}

void test()
{
    
	StuInfo s[MAX] = {
     0 };// Student array 
	int num = 0;// Class size 
	char file[32];
	printf(" Please enter the class file to open :>");
	scanf("%s", &file);
	FILE* fp;
	fp = fopen(file, "r+");

	// If opening fails , Then print “Open Failed!”, And show the reason why the opening failed 
	if (fp == NULL)
	{
    
		printf("Open Failed: % s\n", strerror(errno));
		return;
	}
	// File to "r+" Open and write its contents into the structure , Then close the file , Then open the file in the way required by each function 
	stu_open(file, fp, s, num);
	stu_close(file, fp);

	int input = 0;
	do
	{
    
		menu();
		printf(" Please enter your choice :>");
		scanf("%d", &input);
		switch (input)
		{
    
		case 1:
			stu_byname(file,s,num);
			break;
		case 2:
			stu_add(file,s,num);
			break;
		case 3:
			stu_del(file,s,num);
			break;
		case 4:
			stu_located(file,s,num);
			break;
		case 5:
			stu_multify(file,s,num);
			break;
		case 6:
			stu_show(file,s,num);
			break;
		case 7:
			stu_sort(file,s,num);
			break;
		case 0:
			printf(" About to quit ！ Welcome to use next time ！\n");
			break;
		default:
			printf(" Input error ！ Please re-enter :>\n");
			break;
		}
		stu_close(file, fp);
	} while (input);
}

int main()
{
    
	srand((unsigned int)time(NULL));
	test();
	return 0;
}

5、 summary

Complete a complete project independently for the first time , At the beginning, it was very difficult , I even think I can't finish , But in “ Force ” Slowly groping , Finally, I succeeded .
Today, I will show it in the way of blog , If there is anything wrong , Please don't hesitate to give me some advice , I will listen carefully and correct it in time ！！！