由于作者被舍友求着代写课设，迫于无奈写的，在文件操作中一番挣扎最后写出来勉强运行的东西，有一种重复造轮子的美，直接上代码了

//
// Created by Shanwer on 2023/5/26.
// EMS is short for Employee Management System
//
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
enum sex{female,male};
typedef struct {
    int ID;
    char name[30];
    enum sex s;
    char from[20];
    char department[35];
    char title[30];
    char job[20];
    struct{
        int transferJob;
        int transferDepartment;
        int transferDuty;
        int retirement;//0 for not retired,1 for retired;
    }status;
}employee;

void printEmployee(employee e){
    if(e.s == 0)
        printf("员工信息为:%d %s female %s %s %s %s\n",e.ID,e.name,e.from,e.department,e.title,e.job);
    else
        printf("员工信息为:%d %s male %s %s %s %s\n",e.ID,e.name,e.from,e.department,e.title,e.job);
}

char * getLastIndex(char * s,int whetherInsertSpace){
    //get the last index of string(including the first \0) and decide whether insert a space
    while(*s != '\0'){
        s++;
    }
    if(whetherInsertSpace) {
        *s = ' ';
        s++;
    }
    return s;
}

int registerNewEmployee(){
    FILE *tmpP = NULL;
    tmpP = fopen("employeeInfo.txt", "r");
    employee tmpE;//发现存储的话其实可以直接一个char *更方便点，但是没考虑到
    char buff[sizeof(employee)];
    if(tmpP == NULL){
        printf("打开文件失败\n");//读到最后一行
        return 1;
    }else {
        while(!feof(tmpP)) {
            fgets(buff,sizeof(employee),tmpP);
        }
        REGISTER:
            fclose(tmpP);
            FILE *fp = NULL;
            fp = fopen("employeeInfo.txt", "a");
            char LastID[5];//最多员工人数100000人，故为5
            sscanf(buff,"%[^ ]", LastID);//截取字符串直到第一个空格
            tmpE.ID = atoi(LastID)+1;//stdlib的字符串转整型
            printf("要添加的工号为:%d\n",tmpE.ID);
            printf("输入员工姓名:");
            scanf("%30s", tmpE.name);
            printf("输入员工性别，0为女，1为男:");
            scanf("%d",&tmpE.s);
            printf("输入员工籍贯:");
            scanf("%20s",tmpE.from);
            printf("输入员工部门:");
            scanf("%35s",tmpE.department);
            printf("输入员工职称:");
            scanf("%30s",tmpE.title);
            printf("输入员工职务:");
            scanf("%20s",tmpE.job);
            printEmployee(tmpE);
            printf("确认登记吗，按y确认，其他键取消:");
            char confirm = 'y';
            char tempClearC;
            while((tempClearC = getchar()) != '\n');//清空输入缓冲区
            scanf("%c",&confirm);
            if(confirm == 'y'){
                fputs("\n",fp);//windows换行符为\r\n，但是实际操作发现会换行两次
                char tmpRow[sizeof(employee)];
                itoa(tmpE.ID,tmpRow,10);
                char *tmpRowP = tmpRow;
                tmpRowP = getLastIndex(tmpRowP,1);
                strncpy(tmpRowP,tmpE.name,30);
                tmpRowP = getLastIndex(tmpRowP,1);
                itoa(tmpE.s,tmpRowP,10);
                tmpRowP = getLastIndex(tmpRowP,1);
                strncpy(tmpRowP,tmpE.from,20);
                tmpRowP = getLastIndex(tmpRowP,1);
                strncpy(tmpRowP,tmpE.department,35);
                tmpRowP = getLastIndex(tmpRowP,1);
                strncpy(tmpRowP,tmpE.title,30);
                tmpRowP = getLastIndex(tmpRowP,1);
                strncpy(tmpRowP,tmpE.job,20);
                fputs(tmpRow,fp);
                fclose(fp);
                return 0;
            }else
            memset(&tmpE, 0, sizeof(tmpE));//不确认的话就清空临时结构体
            goto REGISTER;
    }
}

int editEmployee() {
    //修改和删除行非常麻烦，弃坑
    int readID;char tmpBuff[sizeof(employee)];//tmpBuff is written to but never read
    employee tmpE;
    printf("输入要修改的员工工号:");
    scanf("%d", &tmpE.ID);
    FILE *fp = NULL;
    fp = fopen("employeeInfo.txt", "r+");
    for (int i = 0; i < tmpE.ID; i++) {
        fgets(tmpBuff, sizeof(employee), fp);//读取到需求行的上一行，建立在数据文件结构正常的情况下,工号顺序递增，因此顺序读取
    }
    fscanf(fp,"%d",&readID);//读取需求行的工号，以空格截断
    if (tmpE.ID == readID) {
        EDIT:
            printf("输入员工姓名:");
            scanf("%30s", tmpE.name);
            printf("输入员工性别，0为女，1为男:");
            scanf("%d", &tmpE.s);
            printf("输入员工籍贯:");
            scanf("%20s", tmpE.from);
            printf("输入员工部门:");
            scanf("%35s", tmpE.department);
            printf("输入员工职称:");
            scanf("%30s", tmpE.title);
            printf("输入员工职务:");
            scanf("%20s", tmpE.job);
            printEmployee(tmpE);
            printf("确认操作吗，按y确认，其他键取消:");
            char confirm = 'y';
            char tempClearC;
            while ((tempClearC = getchar()) != '\n');//清空输入缓冲区
            confirm = getchar();
            if (confirm == 'y') {
                char tmpRow[sizeof(employee)];
                char *tmpRowP = tmpRow;
                fgets(tmpBuff, sizeof(employee), fp);//读取到末尾
                fseek(fp,-strlen(tmpBuff)+1,SEEK_CUR);//偏移当前行的长度,由于已经取掉了+1防止吞空格，如果超出文件范围则指针不会移动
                strncpy(tmpRowP, tmpE.name, 30);
                tmpRowP = getLastIndex(tmpRowP, 1);
                itoa(tmpE.s, tmpRowP, 10);
                tmpRowP = getLastIndex(tmpRowP, 1);
                strncpy(tmpRowP, tmpE.from, 20);
                tmpRowP = getLastIndex(tmpRowP, 1);
                strncpy(tmpRowP, tmpE.department, 35);
                tmpRowP = getLastIndex(tmpRowP, 1);
                strncpy(tmpRowP, tmpE.title, 30);
                tmpRowP = getLastIndex(tmpRowP, 1);
                strncpy(tmpRowP, tmpE.job, 20);
                fputs(tmpRow, fp);//如果新的字符串比原来的字符串短的话就出问题了
                fclose(fp);
                return 0;
            }
            else {
                memset(&tmpE, 0, sizeof(tmpE));//不确认的话就清空临时结构体
                goto EDIT;
            }
    }else {
        printf("未查找到指定的员工!");
        return 1;
    }
}

int findEmployee() {
    char tmpBuff[sizeof(employee)];
    int ID;int readID;
    printf("输入要查找的员工工号:");
    scanf("%d", &ID);
    FILE *fp = NULL;
    fp = fopen("employeeInfo.txt", "r");
    for (int i = 0; i < ID; i++) {
        fgets(tmpBuff, sizeof(employee), fp);//读取到需求行的这一行，建立在数据文件结构正常的情况下,工号顺序递增，因此顺序读取
    }
    fscanf(fp,"%d",&readID);
    fgetc(fp);
    if(readID == ID){
        fgets(tmpBuff, sizeof(employee),fp);
        puts(tmpBuff);
        return 0;
    }else
    {
        printf("未查找到指定的员工!");
        return 1;
    }
}

int printStatus(){
    findEmployee();
    return 0;
}

int main() {
    //为了逻辑正确，工号不可输入，而是由系统设置，从0递增
    //最多员工人数100000人
    //文件的第一行占用做默认值避免逻辑错误
    //一个功能一个函数
    int input;
    printf("欢迎使用企业人事管理系统\n"
           "1.登记新员工信息\n"
           "2.修改员工信息\n"
           "3.删除员工信息\n"
           "4.查找员工信息\n"
           "5.按工号，部门输出员工职称\n"
           "6.查询员工工作单位变化\n"
           "输入功能前的序号数字来选择功能:");
    scanf("%d", &input);
    while (input < 1 || input > 6) {
        printf("错误的输入，输入功能前的序号数字来选择功能\n");
        printf("输入功能前的序号数字来选择功能:");
        scanf("%d", &input);
    }
    switch (input) {
        case 1:
            if(!registerNewEmployee()) {
                printf("创建成功!");
                break;
            }
            else
                break;
        case 2:
            if(!editEmployee()){
                printf("修改成功!");
                break;
            }
            else
                break;
        case 3:
            //删除的思路是令一个二维字符数组来存储当前文件的所有行，再删除指定的一行，这得上链表，然后再存到临时文件，删除原来文件，复制过去才可以，过于复杂了
            break;
        case 4:
            if(!findEmployee()){
                printf("查找成功");
                break;
            }else
                break;
        case 5:
            findEmployee();//不理解按工号，部门输出员工职称是什么意思
            break;
        case 6:
            printStatus();//查询员工工作单位变化，原理上是输出结构体中嵌套的结构体，由于没有操作，未被初始化，因而不做更多操作
            break;
        default:
            break;
    }
}