/* delete.c：刪除學生信息記錄*/
#include "stdio.h"
void DelRecord()
 {
    int i,j,k;
    long delnum;      /*存放教師輸入的要刪除員工序號*/
    student TmpS;    /*定義進行操作時的臨時結構體變量*/
    student s[SIZE];/*SIZE，在shead.h頭文件中定義的常量，值為100  */
    int recNumber;    /*原文件中的記錄數*/
    char DataFile[40] = "",next;
    /*DataFile存儲學生信息的文件名，next為是否進行下一次刪除操作的選項*/
    FILE *fp;/*====fp指針指向存儲數據的文件名====*/
    printf("\nplease input the name of file where data is stored,end with enter key.\n");
    gets(DataFile);
    /*提示教師輸入要進行刪除紀錄的文件名*/
    while(*DataFile == ('\0'))
    {
        printf("\nplease input the name of file where data is stored,end with enter key.\n");
        gets(DataFile);
    }
begin:
    /*以二進制讀的方式打開文件*/
    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);
    }
    /*輸入要刪除的學生學號*/
    printf("please input the Employee'seatnum which you will delete:");
    scanf("%ld",&delnum);
    printf("the student you will delete is:%ld\n",delnum);
   /*將文件中信息存入結構體數組*/
   /*與要刪除的學生學號相匹配的項不寫入數組，
   循環后數組中即為去掉了要刪除記錄后的剩余記錄*/
   recNumber=0;
    while((fread(&TmpS,sizeof(student),1,fp)) != (int)NULL)
    {
        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);
        /*====將刪除后的剩余結構體記錄寫入文件====*/
        fp=fopen(DataFile,"wb+");
        if (fp == NULL)
        {
            printf("\nSet up file %sfail !end with anykey.\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 with anykey.\n",DataFile);
                perror("Write file fail!");
                    getch();
                    exit(1);
            }
        }
        fclose(fp);
/*====顯示刪除后的文件====*/
    fp=fopen(DataFile,"rb");
    if (fp == NULL)
    {
        printf("\nOpen file%sfail!End with any key \n",DataFile);
        perror("Open file fail");
        getch();
        exit(1);
    }
    printf("the file after delete is:\n");
    printf("\nNumber\tName\tchinesescore\tmathscore\tzongfen\n");
    while(fread(&TmpS,sizeof(student),1,fp) != (int)NULL)
    {
        if(TmpS.Number!=0)
        printf("\n%ld\t%s\%4.1f\t%4.1f\t%4.1f\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;
}