/* modnum.c ：修改學生信息        */
#include "stdio.h"
void ModifyByNumber()
 {
    int i,j,k;
    long modnum;    /*存儲教師輸入的要修改的學生學號*/
    /*輸入各項修改后信息*/
    long Number;
    char Name[20];
    float chinesescore;
    float mathscore;
    float heji;
    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;
    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====*/
    /*提示教師輸入要進行修改記錄的文件名*/
    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修改記錄的文件名*/
    while(*DataFile == ('\0'))
    {
        printf("\nplease input the name of file where data is stored,end with enter key.\n");
        gets(DataFile);
    }
begin:
    /*以讀的方式打開文件，如文件不存在，提示錯誤*/
    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);
    }
    printf("please input the Employee'seatnum which you will modify:");
    scanf("%ld",&modnum);
    printf("the student you will delete is:%ld\n",modnum);
    /*輸入要修改記錄的各項內容值*/
    Number=modnum;
    printf("name=");
    scanf("%s",Name);

    printf("chinesescore=");
    scanf("%f",&chinesescore);

    printf("mathscore=");
    scanf("%f",&mathscore);

    /*用公式自動計算學生總分*/
    heji=chinesescore+mathscore;
   /*將文件中要修改的信息存入結構體數組*/
   recNumber=0;
   /*循環將文件數據讀入結構體數組，
   如文件中的數據學生號和要修改的學生號不符，則原樣寫入數組，
   如文件中數據的學生號和要修改學生號匹配，
   則根據教師輸入的各項修改內容重新賦值，即修改，并寫入數組*/
    while((fread(&TmpS,sizeof(student),1,fp)) != (int)NULL)
    {
        if(TmpS.Number!=modnum)
            {
            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++;
            }
        else
            {
            s[recNumber].Number = Number;
            strcpy(s[recNumber].Name, Name);
            s[recNumber].chinesescore = chinesescore;
            s[recNumber].mathscore = mathscore;
            s[recNumber].heji = heji;
            recNumber++;
            }

    }
    fclose(fp);
   /*====將修改后的結構體數組記錄寫入文件====*/
        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);
     /*====顯示修改后的文件====*/
    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 modify is:\n");
    printf("\nNumber \t\tName\tchinesescore\tmathscore\theji\n");
    while(fread(&TmpS,sizeof(student),1,fp) != (int)NULL)
    {
        if(TmpS.Number!=0)
        printf("\n%ld\t        %s\t   %5.2f\t  %5.2f\t%5.2f\n",TmpS.Number,TmpS.Name,TmpS.chinesescore,TmpS.mathscore,TmpS.heji);
    }
    fclose(fp);
/*提示是否進行下一次修改*/
    printf("\nGo on ?(y/n)");
    next=getche();
    putchar('\n');
    if ( next =='y' || next =='Y') goto begin;
 }