delete.cpp

内有说明

//delete删除学生信息记录
#include "delete.h"

void DelRecord()
{
  int i;
  long delnum;                       //存放教师输入的要删除员工序号
  Student Tmps;                      //定义进行操作时的临时结构体变量
  Student s[SIZE];
  int recNumber;                     //原文件中的记录数
  char DataFile[40] = "", next;      //next为是否进行下一次删除操作的选项
  FILE *fp;
  printf("\nplease input the name of file where data is stored,end with enter key.\n");
  gets(DataFile);

  //提示教师输入要进行删除记录的文件名
  while (*DataFile == ('\0'))
  {
    printf("\nplease input the name of file where data is stored,end with enter key.\n");
    gets(DataFile);
  }

begin:
  //以二进制读的方式发开文件
  fp = fopen(DataFile, "rb");
  if (fp == NULL)
  {
    printf("\nopen file %s fail! end with any key\n", DataFile);
    perror("open file fail");
    getch();
    exit(1);
  }

  //输入要删除的学生的学号
  printf("please input the employee'seatnum which you will delete:");
  scanf("%ld", &delnum);
  printf("the Student you will delete is:%ld\n", delnum);

  //将文件中信息存入结构体数组
  //与要删除的学生学号相匹配的项不写入数组，循环后数组中即为去掉了要删除记录后的剩余记录
  recNumber = 0;
  while ((fread(&Tmps, sizeof(Student), 1, fp)))
  {
    if (Tmps.Number != delnum)
    {
      s[recNumber].Number = Tmps.Number;
      strcpy(s[recNumber].Name, Tmps.Name);
      s[recNumber].chinesescore = Tmps.chinesescore;
      s[recNumber].mathscore = Tmps.mathscore;
      s[recNumber].heji = Tmps.heji;
      recNumber++;
    }
  }

  fclose(fp);

  //===将删除后的剩余结构体记录写入文件=====
  fp = fopen(DataFile, "wb+");
  if (fp == NULL)
  {
    printf("\nset up file %s fail ! end with any key.\n", DataFile);
    perror("set up fail");
    getch();
    exit(1);
  }

  for (i = 0;i < recNumber;i++)
  {
    if (fwrite(&s[i], sizeof(Student), 1, fp) != 1)
    {
      printf("\nwrite file %s fail! end any key", DataFile);
      perror("write file fail");
      getch();
      exit(1);
    }
  }
  fclose(fp);

  //显示删除后的文件
  fp = fopen(DataFile, "rb");
  if (fp == NULL)
  {
    printf("\nopen file %s fail! end any key", DataFile);
    perror("open file fail");
    getch();
    exit(1);
  }

  printf("\nthe file after delete is:\n");
  printf("\nNumber\tName\tchinesescore\tmathscore\tzongfen\n");
  while (fread(&Tmps, sizeof(Student), 1, fp))
  {
    if (Tmps.Number != 0)
      printf("\n%ld\t%s\t%4.1f\t%4.1f\t%4.1f\t\n", Tmps.Number, Tmps.Name, Tmps.chinesescore, Tmps.mathscore, Tmps.heji);
  }
  fclose(fp);

  printf("\ngo on ?(y/n)");
  next = getche();
  putchar('\n');
  if (next == 'y' || next == 'Y')
    goto begin;
}