eak； 案例3： printf（“待替换字符：”）； scanf（“%c”、&d）； printf（“一个新字符：”）； scanf（“%c”和“&n”）； 更新文件（d，n）； 打破 案例4： deletefile（）； 打破 } getchar（）；

eak； 案例3： printf（“待替换字符：”）； scanf（“%c”、&d）； printf（“一个新字符：”）； scanf（“%c”和“&n”）； 更新文件（d，n）； 打破 案例4： deletefile（）； 打破 } getchar（）； 返回0； }

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一致的格式是一个很好的起点。你也应该阅读。并学习如何使用调试器逐步完成代码。

#include<stdio.h>
#include<stdlib.h>

char id[20], year[20], title[20], name[20];
void write(char id[], char title[], char name[], char year[])
{
    FILE *fp;

    fp = fopen("book.txt", "r");

    if(fp == NULL) 
    {
        fp = fopen("book.txt", "w");
        fprintf(fp, "ID TITLE NAME YEAR\n");
        fprintf(fp, "%s\t\t%s\t\t%s\t\t%s\t\t", id, title, name, year);
    }
    else
    {
        fp = fopen("book.txt.", "a");
        fprintf(fp, "%s\t\t%s\t\t%s\t\t%s\t\t", id, title, name, year);
        exit(2);
    }

    fclose(fp);
}
void displayfile()
{
    FILE *fp;

    fp = fopen("book.txt", "r");
    if(fp == NULL)
    {
        printf("there is no data");
    }
    while(!feof(fp))
    {
        fscanf(fp, "%[^#]#%[^#]#%[^#]#%[^#]#%s", id, title, name, year);
        printf("\n%s\t\t\n%s\t\t\n%s\t\t\n%s\t\t", id, title, name, year);

    }
    fclose(fp);
}

void updatefile()
{
    FILE *fp;
    int ch;
    fp = fopen("book.txt", "r+");
    if(fp == NULL)
    {
        fprintf(stderr, "there is no data");
        exit(1);
    }
    while ((ch = fgetc(fp)) !=EOF)
    {
        if(ch == 'i')
        {
            fseek(fp, -1, SEEK_CUR);
            fputc('a', fp);
            fseek(fp, 0, SEEK_CUR);
        }
    }
    fclose(fp);
}

void deletefile()
{
    int apus;
    FILE *fp;

    fp = fopen("book.txt", "r");
}


int  main() {

int option;

    printf("please select one of this : \n");
    printf("1. Input Book Record\n");
    printf("2. Display Book Record\n");
    printf("3. Update Book Record\n");
    printf("4. Erase Book Record\n");
    scanf("%d", &option);

    switch(option)
    {
    case 1:
       printf("Book ID?");
       scanf("%s", id);
       printf("Book title?");
       scanf("%s", title);
       printf("author name?");
       scanf("%s", name);
       printf("year published?");
       scanf("%s", year);
       write(id, title, name, year);
       break;
    case 2:
        displayfile();

    break;
    case 3:
        updatefile();


   }


getchar();

return 0;
}

#include<stdio.h>
#include<stdlib.h>

char id[20], year[20], title[20], name[20];

void writeTofile(char id[], char title[], char name[], char year[])
{
    FILE *fp;
    fp = fopen("book.txt", "a"); // if the file is not exist, it will create it.
                                // do not forget the \n not a new line 
    fprintf(fp, "%s\t%s\t%s\t%s\n", id, title, name, year);
    fclose(fp);
    exit(2);
}

void displayfile()
{
    FILE *fp;

    fp = fopen("book.txt", "r");
    if(fp == NULL)
    {
        fprintf(stderr, "there is no data");
        exit(1);
    } 

    while(!feof(fp))
    {
        fscanf(fp, "%s %s %s %s", id, title, name, year);
        printf("%s: %s\t%s\t%s\n", id, title, name, year);

    } 
    fclose(fp);
}

void updatefile(char d, char n)
{
    // open the book.txt for read
    // open the temp.txt for write
    // move all the char from the book.txt to temp.txt
    // up to the location where you want to change
    // Now add the new chars to the temp file
    // continue copying 
    // close the book.txt 
    // open it again for write (to delete its content)
    //copy temp to the book.txt
    // doen

}

void deletefile()
{
int apus;
FILE *fp;

// if you want to delete the file use
// remove("book.txt"), BUT 
//  if you want to empty the file use 
//(opening he file with white will delete its content )
fp = fopen("book.txt", "w"); 

}


int  main() {

int option;
char d, n;

    printf("please select one of this : \n");
    printf("1. Input Book Record\n");
    printf("2. Display Book Record\n");
    printf("3. Update Book Record\n");
    printf("4. Erase Book Record\n");
    scanf("%d", &option);

    switch(option)
    {
    case 1:
       printf("Book ID?");
       scanf("%s", id);
       printf("Book title?");
       scanf("%s", title);
       printf("author name?");
       scanf("%s", name);
       printf("year published?");
       scanf("%s", year);
       writeTofile(id, title, name, year);
       break;
    case 2:
        displayfile();

    break;
    case 3:
        printf("Character to be replaced: ");
        scanf("%c", &d);
        printf("A new character: ");
        scanf("%c", &n);
        updatefile(d, n);
    break;
    case 4:
        deletefile();
    break;
   }


getchar();

return 0;
}